Full text search engines like Apache Lucene are very powerful technologies to add efficient free text search capabilities to applications. However, Lucene suffers several mismatches when dealing with object domain models. Amongst other things indexes have to be kept up to date and mismatches between index structure and domain model as well as query mismatches have to be avoided.
Hibernate Search addresses these shortcomings - it indexes your domain model with the help of a few annotations, takes care of database/index synchronization and brings back regular managed objects from free text queries. To achieve this Hibernate Search is combining the power of Hibernate and Apache Lucene.
Welcome to Hibernate Search. The following chapter will guide you through the initial steps required to integrate Hibernate Search into an existing Hibernate enabled application. In case you are a Hibernate new timer we recommend you start here.
Table 1.1. System requirements
Java Runtime | A JDK or JRE version 6 or greater. You can download a Java Runtime for Windows/Linux/Solaris here. If using Java version 7 make sure you avoid builds 0 and 1: those versions contained an optimisation bug which would be triggered by Lucene. Hibernate Search 3.x was compatible with Java version 5. |
Hibernate Search | hibernate-search-4.4.6.Final.jar and all
runtime dependencies. You can get the jar artifacts either from
the dist/lib directory of the Hibernate
Search distribution or you can download them from the
JBoss
maven repository. |
Hibernate Core | You will need hibernate-core-4.2.7.SP1.jar
and its transitive dependencies (either from the distribution
bundle or the maven repository). |
JPA 2 | Even though Hibernate Search can be used without JPA
annotations the following instructions will use them for basic
entity configuration (@Entity, @Id,
@OneToMany,...). This part of the configuration could
also be expressed in xml or code. Hibernate Search, however, has also its own set of annotations (@Indexed, @DocumentId, @Field,...) for which there exists so far no XML based alternative; a better option is the Section 4.7, “Programmatic API”. |
The Hibernate Search artifacts can be found in Maven's central
repository but are released first in the JBoss
maven repository. So it's not a requirement but we recommend to
add this repository to your settings.xml file
(see
also Maven
Getting Started for more details).
This is all you need to add to your pom.xml to get started:
Example 1.1. Maven artifact identifier for Hibernate Search
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-search</artifactId>
<version>4.4.6.Final</version>
</dependency>
Example 1.2. Optional Maven dependencies for Hibernate Search
<dependency>
<!-- If using JPA (2), add: -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.2.7.SP1</version>
</dependency>
<!-- Additional Analyzers: -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-search-analyzers</artifactId>
<version>4.4.6.Final</version>
</dependency>
<!-- Infinispan integration: -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-search-infinispan</artifactId>
<version>4.4.6.Final</version>
</dependency>
Only the hibernate-search dependency is mandatory. hibernate-entitymanager is only required if you want to use Hibernate Search in conjunction with JPA.
To use hibernate-search-infinispan, adding the
JBoss Maven repository is mandatory, because it contains the needed
Infinispan dependencies which are currently not mirrored by
central
.
Once you have downloaded and added all required dependencies to your
application you have to add a couple of properties to your hibernate
configuration file. If you are using Hibernate directly this can be done
in hibernate.properties
or
hibernate.cfg.xml
. If you are using Hibernate via JPA
you can also add the properties to persistence.xml
. The
good news is that for standard use most properties offer a sensible
default. An example persistence.xml
configuration
could look like this:
Example 1.3. Basic configuration options to be added to
,
hibernate.properties
or
hibernate.cfg.xml
persistence.xml
...
<property name="hibernate.search.default.directory_provider"
value="filesystem"/>
<property name="hibernate.search.default.indexBase"
value="/var/lucene/indexes"/>
...
First you have to tell Hibernate Search which
DirectoryProvider
to use. This can be achieved by
setting the hibernate.search.default.directory_provider
property. Apache Lucene has the notion of a Directory
to store the index files. Hibernate Search handles the initialization and
configuration of a Lucene Directory
instance via a
DirectoryProvider
. In this tutorial we will use a a
directory provider storing the index in the file system. This will give us
the ability to physically inspect the Lucene indexes created by Hibernate
Search (eg via Luke).
Once you have a working configuration you can start experimenting with
other directory providers (see Section 3.3, “Directory configuration”). Next to the directory
provider you also have to specify the default base directory for all
indexes via hibernate.search.default.indexBase
.
Lets assume that your application contains the Hibernate managed
classes example.Book
and
example.Author
and you want to add free text search
capabilities to your application in order to search the books contained in
your database.
Example 1.4. Example entities Book and Author before adding Hibernate Search specific annotations
package example;
...
@Entity
public class Book {
@Id
@GeneratedValue
private Integer id;
private String title;
private String subtitle;
@ManyToMany
private Set<Author> authors = new HashSet<Author>();
private Date publicationDate;
public Book() {}
// standard getters/setters follow here
...
}
package example;
...
@Entity
public class Author {
@Id
@GeneratedValue
private Integer id;
private String name;
public Author() {}
// standard getters/setters follow here
...
}
To achieve this you have to add a few annotations to the
Book
and Author
class. The
first annotation @Indexed
marks
Book
as indexable. By design Hibernate Search needs
to store an untokenized id in the index to ensure index unicity for a
given entity. @DocumentId
marks the property to use for
this purpose and is in most cases the same as the database primary key.
The @DocumentId
annotation is optional in the case
where an @Id
annotation exists.
Next you have to mark the fields you want to make searchable. Let's
start with title
and subtitle
and
annotate both with @Field
. The parameter
index=Index.YES
will ensure that the text will be
indexed, while analyze=Analyze.YES
ensures that the
text will be analyzed using the default Lucene analyzer. Usually,
analyzing means chunking a sentence into individual words and potentially
excluding common words like 'a'
or
'the
'. We will talk more about analyzers a little later
on. The third parameter we specify within
@Field
, store=Store.NO
, ensures that
the actual data will not be stored in the index. Whether this data is
stored in the index or not has nothing to do with the ability to search
for it. From Lucene's perspective it is not necessary to keep the data
once the index is created. The benefit of storing it is the ability to
retrieve it via projections ( see Section 5.1.3.5, “Projection”).
Without projections, Hibernate Search will per default execute a Lucene query in order to find the database identifiers of the entities matching the query critera and use these identifiers to retrieve managed objects from the database. The decision for or against projection has to be made on a case to case basis. The default behaviour is recommended since it returns managed objects whereas projections only return object arrays.
Note that index=Index.YES
,
analyze=Analyze.YES
and
store=Store.NO
are the default values for these
paramters and could be ommited.
After this short look under the hood let's go back to annotating the
Book
class. Another annotation we have not yet
discussed is @DateBridge
. This annotation is one of the
built-in field bridges in Hibernate Search. The Lucene index is purely
string based. For this reason Hibernate Search must convert the data types
of the indexed fields to strings and vice versa. A range of predefined
bridges are provided, including the DateBridge
which will convert a java.util.Date
into a
String
with the specified resolution. For more
details see Section 4.4, “Bridges”.
This leaves us with @IndexedEmbedded.
This
annotation is used to index associated entities
(@ManyToMany
, @*ToOne
,
@Embedded
and @ElementCollection
) as
part of the owning entity. This is needed since a Lucene index document is
a flat data structure which does not know anything about object relations.
To ensure that the authors' name will be searchable you have to make sure
that the names are indexed as part of the book itself. On top of
@IndexedEmbedded
you will also have to mark all fields
of the associated entity you want to have included in the index with
@Indexed
. For more details see Section 4.1.3, “Embedded and associated objects”.
These settings should be sufficient for now. For more details on entity mapping refer to Section 4.1, “Mapping an entity”.
Example 1.5. Example entities after adding Hibernate Search annotations
package example;
...
@Entity @Indexed
public class Book {
@Id
@GeneratedValue
private Integer id;
@Field(index=Index.YES, analyze=Analyze.YES, store=Store.NO)
private String title;
@Field(index=Index.YES, analyze=Analyze.YES, store=Store.NO)
private String subtitle;
@Field(index = Index.YES, analyze=Analyze.NO, store = Store.YES) @DateBridge(resolution = Resolution.DAY)
private Date publicationDate;
@IndexedEmbedded
@ManyToMany
private Set<Author> authors = new HashSet<Author>();
public Book() {
}
// standard getters/setters follow here
...
}
package example;
...
@Entity
public class Author {
@Id
@GeneratedValue
private Integer id;
@Field
private String name;
public Author() {
}
// standard getters/setters follow here
...
}
Hibernate Search will transparently index every entity persisted, updated or removed through Hibernate Core. However, you have to create an initial Lucene index for the data already present in your database. Once you have added the above properties and annotations it is time to trigger an initial batch index of your books. You can achieve this by using one of the following code snippets (see also Section 6.3, “Rebuilding the whole index”):
Example 1.6. Using Hibernate Session to index data
FullTextSession fullTextSession = Search.getFullTextSession(session);
fullTextSession.createIndexer().startAndWait();
Example 1.7. Using JPA to index data
EntityManager em = entityManagerFactory.createEntityManager();
FullTextEntityManager fullTextEntityManager = Search.getFullTextEntityManager(em);
fullTextEntityManager.createIndexer().startAndWait();
After executing the above code, you should be able to see a Lucene
index under /var/lucene/indexes/example.Book
. Go ahead
an inspect this index with Luke. It will help you to
understand how Hibernate Search works.
Now it is time to execute a first search. The general approach is to
create a Lucene query, either via the Lucene API (Section 5.1.1, “Building a Lucene query using the Lucene API”) or via the Hibernate Search query DSL
(Section 5.1.2, “Building a Lucene query with the Hibernate Search query
DSL”), and then wrap this query into a
org.hibernate.Query
in order to get all the
functionality one is used to from the Hibernate API. The following code
will prepare a query against the indexed fields, execute it and return a
list of Book
s.
Example 1.8. Using Hibernate Session to create and execute a search
FullTextSession fullTextSession = Search.getFullTextSession(session);
Transaction tx = fullTextSession.beginTransaction();
// create native Lucene query unsing the query DSL
// alternatively you can write the Lucene query using the Lucene query parser
// or the Lucene programmatic API. The Hibernate Search DSL is recommended though
QueryBuilder qb = fullTextSession.getSearchFactory()
.buildQueryBuilder().forEntity(Book.class).get();
org.apache.lucene.search.Query query = qb
.keyword()
.onFields("title", "subtitle", "authors.name")
.matching("Java rocks!")
.createQuery();
// wrap Lucene query in a org.hibernate.Query
org.hibernate.Query hibQuery =
fullTextSession.createFullTextQuery(query, Book.class);
// execute search
List result = hibQuery.list();
tx.commit();
session.close();
Example 1.9. Using JPA to create and execute a search
EntityManager em = entityManagerFactory.createEntityManager();
FullTextEntityManager fullTextEntityManager =
org.hibernate.search.jpa.Search.getFullTextEntityManager(em);
em.getTransaction().begin();
// create native Lucene query unsing the query DSL
// alternatively you can write the Lucene query using the Lucene query parser
// or the Lucene programmatic API. The Hibernate Search DSL is recommended though
QueryBuilder qb = fullTextEntityManager.getSearchFactory()
.buildQueryBuilder().forEntity(Book.class).get();
org.apache.lucene.search.Query query = qb
.keyword()
.onFields("title", "subtitle", "authors.name")
.matching("Java rocks!")
.createQuery();
// wrap Lucene query in a javax.persistence.Query
javax.persistence.Query persistenceQuery =
fullTextEntityManager.createFullTextQuery(query, Book.class);
// execute search
List result = persistenceQuery.getResultList();
em.getTransaction().commit();
em.close();
Let's make things a little more interesting now. Assume that one of your indexed book entities has the title "Refactoring: Improving the Design of Existing Code" and you want to get hits for all of the following queries: "refactor", "refactors", "refactored" and "refactoring". In Lucene this can be achieved by choosing an analyzer class which applies word stemming during the indexing as well as the search process. Hibernate Search offers several ways to configure the analyzer to be used (see Section 4.3.1, “Default analyzer and analyzer by class”):
Setting the hibernate.search.analyzer
property in the configuration file. The specified class will then be
the default analyzer.
Setting the
annotation at the entity level.@Analyzer
Setting the @
annotation at the field level.Analyzer
When using the @Analyzer
annotation one can
either specify the fully qualified classname of the analyzer to use or one
can refer to an analyzer definition defined by the
@AnalyzerDef
annotation. In the latter case the Solr
analyzer framework with its factories approach is utilized. To find out
more about the factory classes available you can either browse the Solr
JavaDoc or read the corresponding section on the Solr
Wiki.
In the example below a
StandardTokenizerFactory
is used followed by two
filter factories, LowerCaseFilterFactory
and
SnowballPorterFilterFactory
. The standard tokenizer
splits words at punctuation characters and hyphens while keeping email
addresses and internet hostnames intact. It is a good general purpose
tokenizer. The lowercase filter lowercases the letters in each token
whereas the snowball filter finally applies language specific
stemming.
Generally, when using the Solr framework you have to start with a tokenizer followed by an arbitrary number of filters.
Example 1.10. Using @AnalyzerDef
and the Solr framework
to define and use an analyzer
@Entity
@Indexed @AnalyzerDef(name = "customanalyzer", tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class), filters = { @TokenFilterDef(factory = LowerCaseFilterFactory.class), @TokenFilterDef(factory = SnowballPorterFilterFactory.class, params = { @Parameter(name = "language", value = "English") }) })
public class Book {
@Id
@GeneratedValue
@DocumentId
private Integer id;
@Field
@Analyzer(definition = "customanalyzer")
private String title;
@Field
@Analyzer(definition = "customanalyzer")
private String subtitle;
@IndexedEmbedded
@ManyToMany
private Set<Author> authors = new HashSet<Author>();
@Field(index = Index.YES, analyze = Analyze.NO, store = Store.YES)
@DateBridge(resolution = Resolution.DAY)
private Date publicationDate;
public Book() {
}
// standard getters/setters follow here
...
}
Using @AnalyzerDef
only defines an Analyzer,
you still have to apply it to entities and or properties using
@Analyzer
. Like in the above example the
customanalyzer
is defined but not applied on the
entity: it's applied on the title
and
subtitle
properties only. An analyzer definition is
global, so you can define it on any entity and reuse the definition on
other entities.
The above paragraphs helped you getting an overview of Hibernate Search. The next step after this tutorial is to get more familiar with the overall architecture of Hibernate Search (Chapter 2, Architecture) and explore the basic features in more detail. Two topics which were only briefly touched in this tutorial were analyzer configuration (Section 4.3.1, “Default analyzer and analyzer by class”) and field bridges (Section 4.4, “Bridges”). Both are important features required for more fine-grained indexing. More advanced topics cover clustering (Section 3.4.1, “JMS Master/Slave back end”, Section 3.3.1, “Infinispan Directory configuration”) and large index handling (Section 10.4, “Sharding indexes”).
Hibernate Search consists of an indexing component as well as an index search component. Both are backed by Apache Lucene.
Each time an entity is inserted, updated or removed in/from the
database, Hibernate Search keeps track of this event (through the
Hibernate event system) and schedules an index update. All these updates
are handled without you having to interact with the Apache Lucene APIs
directly (see Section 3.1, “Enabling Hibernate Search and automatic indexing”). Instead, the
interaction with the underlying Lucene indexes is handled via so called
IndexManager
s.
Each Lucene index is managed by one index manager which is uniquely
identified by name. In most cases there is also a one to one relationship
between an indexed entity and a single
IndexManager
. The exceptions are the use cases of
index sharding and index sharing. The former can be applied when the index
for a single entity becomes too big and indexing operations are slowing
down the application. In this case a single entity is indexed into
multiple indexes each with its own index manager (see Section 10.4, “Sharding indexes”). The latter, index
sharing, is the ability to index multiple entities into the same Lucene
index (see Section 10.5, “Sharing indexes”).
The index manager abstracts from the specific index configuration.
In the case of the default index manager this includes details about the
selected backend, the configured reader strategy and the chosen
DirectoryProvider
. These components will be
discussed in greater detail later on. It is recommended that you start
with the default index manager which uses different Lucene
Directory
types to manage the indexes (see Section 3.3, “Directory configuration”). You can, however, also
provide your own IndexManager
implementation (see
Section 3.2, “Configuring the IndexManager
”).
Once the index is created, you can search for entities and return
lists of managed entities saving you the tedious object to Lucene
Document
mapping. The same persistence context is
shared between Hibernate and Hibernate Search. As a matter of fact, the
FullTextSession
is built on top of the Hibernate
Session
so that the application code can use the
unified org.hibernate.Query
or
javax.persistence.Query
APIs exactly the same way a
HQL, JPA-QL or native query would do.
To be more efficient Hibernate Search batches the write interactions
with the Lucene index. This batching is the responsibility of the
Worker
. There are currently two types of batching.
Outside a transaction, the index update operation is executed right after
the actual database operation. This is really a no batching setup. In the
case of an ongoing transaction, the index update operation is scheduled
for the transaction commit phase and discarded in case of transaction
rollback. The batching scope is the transaction. There are two immediate
benefits:
Performance: Lucene indexing works better when operation are executed in batch.
ACIDity: The work executed has the same scoping as the one executed by the database transaction and is executed if and only if the transaction is committed. This is not ACID in the strict sense of it, but ACID behavior is rarely useful for full text search indexes since they can be rebuilt from the source at any time.
You can think of those two batch modes (no scope vs transactional) as the equivalent of the (infamous) autocommit vs transactional behavior. From a performance perspective, the in transaction mode is recommended. The scoping choice is made transparently. Hibernate Search detects the presence of a transaction and adjust the scoping (see Section 3.4, “Worker configuration”).
It is recommended - for both your database and Hibernate Search - to execute your operations in a transaction, be it JDBC or JTA.
Hibernate Search works perfectly fine in the Hibernate / EntityManager long conversation pattern aka. atomic conversation.
Hibernate Search offers the ability to let the batched work being
processed by different back ends. Several back ends are provided out of
the box and you have the option to plugin your own. It is important to
understand that in this context back end encompasses more than just the
configuration option
hibernate.search.default.worker.backend
. This property
just specifies a implementation of the
BackendQueueProcessor
interface which is a part of
a back end configuration. In most cases, however, additional configuration
settings are needed to successfully configure a specific backend setup,
like for example the JMS back end.
In this mode, all index update operations applied on a given node (JVM) will be executed to the Lucene directories (through the directory providers) by the same node. This mode is typically used in non clustered environment or in clustered environments where the directory store is shared.
This mode targets non clustered applications, or clustered
applications where the Directory
is taking care
of the locking strategy.
The main advantage is simplicity and immediate visibility of the changes in Lucene queries (a requirement in some applications).
An alternative back end viable for non-clustered and non-shared index configurations is the near-real-time backend.
All index update operations applied on a given node are sent to a JMS queue. A unique reader will then process the queue and update the master index. The master index is then replicated on a regular basis to the slave copies. This is known as the master/slaves pattern. The master is the sole responsible for updating the Lucene index. The slaves can accept read as well as write operations. However, they only process the read operation on their local index copy and delegate the update operations to the master.
This mode targets clustered environments where throughput is critical, and index update delays are affordable. Reliability is ensured by the JMS provider and by having the slaves working on a local copy of the index.
The JGroups based back end works similar to the JMS one and is designed after the same master/slave pattern. However, instead of JMS the JGroups toolkit is used as a replication mechanism. This back end can be used as an alternative to JMS when response time is critical, but i.e. JNDI service is not available.
Note that while JMS can usually be configured to use persistent queues, JGroups talks directly to other nodes over network. Message delivery to other reachable nodes is guaranteed, but if no master node is available, index operations are silently discarded. This backend can be configured to use asynchronous messages, or to wait for each indexing operation to be completed on the remote node before returning.
The JGroups backend can be configured with static master or slave roles, or can be setup to perform an auto-election of the master. This mode is particularly useful to have the system automatically pick a new master in case of failure, but during a reelection process some indexing operations might be lost. For this reason this mode is not suited for use cases requiring strong consistency guarantees. When configured to perform an automatic election, the master node is defined as an hash on the index name: the role is therefore possibly different for each index or shard.
When executing a query, Hibernate Search interacts with the Apache Lucene indexes through a reader strategy. Choosing a reader strategy will depend on the profile of the application (frequent updates, read mostly, asynchronous index update etc). See also Section 3.5, “Reader strategy configuration”
With this strategy, Hibernate Search will share the same
IndexReader
, for a given Lucene index, across
multiple queries and threads provided that the
IndexReader
is still up-to-date. If the
IndexReader
is not up-to-date, a new one is
opened and provided. Each IndexReader
is made of
several SegmentReader
s. This strategy only
reopens segments that have been modified or created after last opening
and shares the already loaded segments from the previous instance. This
strategy is the default.
The name of this strategy is shared
.
Every time a query is executed, a Lucene
IndexReader
is opened. This strategy is not the
most efficient since opening and warming up an
IndexReader
can be a relatively expensive
operation.
The name of this strategy is not-shared
.
Let's start with the most basic configuration question - how do I enable Hibernate Search?
The good news is that Hibernate Search is enabled out of the box
when detected on the classpath by Hibernate Core. If, for some reason
you need to disable it, set
hibernate.search.autoregister_listeners
to
false
. Note that there is no performance penalty
when the listeners are enabled but no entities are annotated as
indexed.
By default, every time an object is inserted, updated or deleted through Hibernate, Hibernate Search updates the according Lucene index. It is sometimes desirable to disable that features if either your index is read-only or if index updates are done in a batch way (see Section 6.3, “Rebuilding the whole index”).
To disable event based indexing, set
hibernate.search.indexing_strategy = manual
In most case, the JMS backend provides the best of both world, a lightweight event based system keeps track of all changes in the system, and the heavyweight indexing process is done by a separate process or machine.
The role of the index manager component is described in Chapter 2, Architecture. Hibernate Search provides two possible implementations for this interface to choose from.
directory-based
: the default implementation
which uses the Lucene Directory
abstraction to
manage index files.
near-real-time
: avoid flushing writes to disk
at each commit. This index manager is also
Directory
based, but also makes uses of
Lucene's NRT functionality.
To select an alternative you specify the property:
hibernate.search.[default|<indexname>].indexmanager = near-real-time
The default IndexManager
implementation.
This is the one mostly referred to in this documentation. It is highly
configurable and allows you to select different settings for the reader
strategy, back ends and directory providers. Refer to Section 3.3, “Directory configuration”, Section 3.4, “Worker configuration” and Section 3.5, “Reader strategy configuration” for more details.
The NRTIndexManager
is an extension of the
default IndexManager
, leveraging the Lucene NRT
(Near Real Time) features for extreme low latency index writes. As a
tradeoff it requires a non-clustered and non-shared index. In other
words, it will ignore configuration settings for alternative back ends
other than lucene
and will acquire exclusive write
locks on the Directory
.
To achieve this low latency writes, the
IndexWriter
will not flush every change to disk.
Queries will be allowed to read updated state from the unflushed index
writer buffers; the downside of this strategy is that if the application
crashes or the IndexWriter
is otherwise killed
you'll have to rebuild the indexes as some updates might be lost.
Because of these downsides, and because a master node in cluster can be configured for good performance as well, the NRT configuration is only recommended for non clustered websites with a limited amount of data.
It is also possible to configure a custom
IndexManager
implementation by specifying the
fully qualified class name of your custom implementation. This
implementation must have a no-argument constructor:
hibernate.search.[default|<indexname>].indexmanager = my.corp.myapp.CustomIndexManager
Your custom index manager implementation doesn't need to use the
same components as the default implementations. For example, you can
delegate to a remote indexing service which doesn't expose a
Directory
interface.
As we have seen in Section 3.2, “Configuring the IndexManager
” the
default index manager uses Lucene's notion of a
Directory
to store the index files. The
Directory
implementation can be customized and
Lucene comes bundled with a file system and an in-memory implementation.
DirectoryProvider
is the Hibernate Search
abstraction around a Lucene Directory
and handles
the configuration and the initialization of the underlying Lucene
resources. Table 3.1, “List of built-in DirectoryProvider
” shows the list of
the directory providers available in Hibernate Search together with their
corresponding options.
To configure your DirectoryProvider
you have
to understand that each indexed entity is associated to a Lucene index
(except of the case where multiple entities share the same index - Section 10.5, “Sharing indexes”). The name of the index is given by
the index
property of the
@Indexed
annotation. If the
index
property is not specified the fully qualified
name of the indexed class will be used as name (recommended).
Knowing the index name, you can configure the directory provider and
any additional options by using the prefix
hibernate.search.
<indexname>
.
The name default
(hibernate.search.default
) is reserved and can be
used to define properties which apply to all indexes. Example 3.2, “Configuring directory providers” shows how
hibernate.search.default.directory_provider
is used
to set the default directory provider to be the filesystem one.
hibernate.search.default.indexBase
sets then the
default base directory for the indexes. As a result the index for the
entity Status
is created in
/usr/lucene/indexes/org.hibernate.example.Status
.
The index for the Rule
entity, however, is
using an in-memory directory, because the default directory provider for
this entity is overridden by the property
hibernate.search.Rules.directory_provider
.
Finally the Action
entity uses a custom
directory provider CustomDirectoryProvider
specified via
hibernate.search.Actions.directory_provider
.
Example 3.1. Specifying the index name
package org.hibernate.example;
@Indexed
public class Status { ... }
@Indexed(index="Rules")
public class Rule { ... }
@Indexed(index="Actions")
public class Action { ... }
Example 3.2. Configuring directory providers
hibernate.search.default.directory_provider = filesystem hibernate.search.default.indexBase = /usr/lucene/indexes hibernate.search.Rules.directory_provider = ram hibernate.search.Actions.directory_provider = com.acme.hibernate.CustomDirectoryProvider
Using the described configuration scheme you can easily define common rules like the directory provider and base directory, and override those defaults later on on a per index basis.
Table 3.1. List of built-in DirectoryProvider
Name and description | Properties |
---|---|
ram: Memory based directory, the
directory will be uniquely identified (in the same deployment
unit) by the @Indexed.index element | none |
filesystem: File system based directory. The directory used will be <indexBase>/< indexName > |
|
filesystem-master: File system
based directory. Like The recommended value for the refresh period is (at least) 50% higher that the time to copy the information (default 3600 seconds - 60 minutes). Note that the copy is based on an incremental copy mechanism reducing the average copy time. DirectoryProvider typically used on the master node in a JMS back end cluster. The
|
|
filesystem-slave: File system
based directory. Like The recommended value for the refresh period is (at least) 50% higher that the time to copy the information (default 3600 seconds - 60 minutes). Note that the
copy is based on an incremental copy mechanism reducing the
average copy time. If a copy is still in progress when
DirectoryProvider typically used on slave nodes using a JMS back end. The
|
|
infinispan: Infinispan based directory. Use it to store the index in a distributed grid, making index changes visible to all elements of the cluster very quickly. Also see Section 3.3.1, “Infinispan Directory configuration” for additional requirements and configuration settings. Infinispan needs a global configuration and additional dependencies; the settings defined here apply to each different index. |
|
If the built-in directory providers do not fit your needs, you can
write your own directory provider by implementing the
org.hibernate.store.DirectoryProvider
interface.
In this case, pass the fully qualified class name of your provider into
the directory_provider
property. You can pass any
additional properties using the prefix
hibernate.search.
<indexname>
.
Infinispan is a distributed, scalable, highly available data grid platform which supports autodiscovery of peer nodes. Using Infinispan and Hibernate Search in combination, it is possible to store the Lucene index in a distributed environment where index updates are quickly available on all nodes.
This section describes in greater detail how to configure Hibernate Search to use an Infinispan Lucene Directory.
When using an Infinispan Directory the index is stored in memory and shared across multiple nodes. It is considered a single directory distributed across all participating nodes. If a node updates the index, all other nodes are updated as well. Updates on one node can be immediately searched for in the whole cluster.
The default configuration replicates all data defining the index across all nodes, thus consuming a significant amount of memory. For large indexes it's suggested to enable data distribution, so that each piece of information is replicated to a subset of all cluster members.
It is also possible to offload part or most information to a
CacheStore
, such as plain filesystem, Amazon S3,
Cassandra, Berkley DB or standard relational databases. You can
configure it to have a CacheStore
on each node or
have a single centralized one shared by each node.
See the Infinispan documentation for all Infinispan configuration options.
To use the Infinispan directory via Maven, add the following dependencies:
Example 3.3. Maven dependencies for Hibernate Search
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-search</artifactId>
<version>4.4.6.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-search-infinispan</artifactId>
<version>4.4.6.Final</version>
</dependency>
For the non-maven users, add
hibernate-search-infinispan.jar
,
infinispan-lucene-directory.jar
and
infinispan-core.jar
to your application classpath.
These last two jars are distributed by Infinispan.
Even when using an Infinispan directory it's still recommended
to use the JMS Master/Slave or JGroups backend, because in Infinispan
all nodes will share the same index and it is likely that
IndexWriter
s being active on different nodes
will try to acquire the lock on the same index. So instead of sending
updates directly to the index, send it to a JMS queue or JGroups
channel and have a single node apply all changes on behalf of all
other nodes.
Configuring a non-default backend is not a requirement but a performance optimization as locks are enabled to have a single node writing.
To configure a JMS slave only the backend must be replaced, the
directory provider must be set to infinispan
; set
the same directory provider on the master, they will connect without
the need to setup the copy job across nodes. Using the JGroups backend
is very similar - just combine the backend configuration with the
infinispan
directory provider.
The most simple configuration only requires to enable the backend:
hibernate.search.[default|<indexname>].directory_provider = infinispan
That's all what is needed to get a cluster-replicated index, but the default configuration does not enable any form of permanent persistence for the index; to enable such a feature an Infinispan configuration file should be provided.
To use Infinispan, Hibernate Search requires a
CacheManager
; it can lookup and reuse an
existing CacheManager,
via JNDI, or start and
manage a new one. In the latter case Hibernate Search will start and
stop it ( closing occurs when the Hibernate
SessionFactory
is closed).
To use and existing CacheManager
via JNDI
(optional parameter):
hibernate.search.infinispan.cachemanager_jndiname = [jndiname]
To start a new CacheManager
from a
configuration file (optional parameter):
hibernate.search.infinispan.configuration_resourcename = [infinispan configuration filename]
If both parameters are defined, JNDI will have priority. If none
of these is defined, Hibernate Search will use the default Infinispan
configuration included in
hibernate-search-infinispan.jar
. This configuration
should work fine in most cases but does not store the index in a
persistent cache store.
As mentioned in Table 3.1, “List of built-in DirectoryProvider
”, each
index makes use of three caches, so three different caches should be
configured as shown in the
default-hibernatesearch-infinispan.xml
provided in
the hibernate-search-infinispan.jar
. Several
indexes can share the same caches.
It is possible to refine how Hibernate Search interacts with Lucene through the worker configuration. There exist several architectural components and possible extension points. Let's have a closer look.
First there is a Worker
. An implementation of
the Worker
interface is responsible for receiving
all entity changes, queuing them by context and applying them once a
context ends. The most intuitive context, especially in connection with
ORM, is the transaction. For this reason Hibernate Search will per default
use the TransactionalWorker
to scope all changes
per transaction. One can, however, imagine a scenario where the context
depends for example on the number of entity changes or some other
application (lifecycle) events. For this reason the
Worker
implementation is configurable as shown in
Table 3.2, “Scope configuration”.
Table 3.2. Scope configuration
Property | Description |
hibernate.search.worker.scope | The fully qualified class name of the
Worker implementation to use. If this
property is not set, empty or transaction the
default TransactionalWorker is
used. |
hibernate.search.worker.* | All configuration properties prefixed with
hibernate.search.worker are passed to the
Worker during initialization. This allows adding custom, worker
specific parameters. |
Once a context ends it is time to prepare and apply the index changes. This can be done synchronously or asynchronously from within a new thread. Synchronous updates have the advantage that the index is at all times in sync with the databases. Asynchronous updates, on the other hand, can help to minimize the user response time. The drawback is potential discrepancies between database and index states. Lets look at the configuration options shown in Table 3.3, “Execution configuration”.
The following options can be different on each index; in fact they
need the indexName prefix or use default
to set the
default value for all indexes.
Table 3.3. Execution configuration
Property | Description |
hibernate.search.<indexName>.worker.execution |
|
hibernate.search.<indexName>.worker.thread_pool.size | The backend can apply updates from the same transaction context (or batch) in parallel, using a threadpool. The default value is 1. You can experiment with larger values if you have many operations per transaction. |
hibernate.search.<indexName>.worker.buffer_queue.max | Defines the maximal number of work queue if the thread poll is starved. Useful only for asynchronous execution. Default to infinite. If the limit is reached, the work is done by the main thread. |
So far all work is done within the same Virtual Machine (VM), no matter which execution mode. The total amount of work has not changed for the single VM. Luckily there is a better approach, namely delegation. It is possible to send the indexing work to a different server by configuring hibernate.search.default.worker.backend - see Table 3.4, “Backend configuration”. Again this option can be configured differently for each index.
Table 3.4. Backend configuration
Property | Description |
hibernate.search.<indexName>.worker.backend |
You can also
specify the fully qualified name of a class implementing
|
Table 3.5. JMS backend configuration
Property | Description |
hibernate.search.<indexName>.worker.jndi.* | Defines the JNDI properties to initiate the InitialContext (if needed). JNDI is only used by the JMS back end. |
hibernate.search.<indexName>.worker.jms.connection_factory | Mandatory for the JMS back end. Defines the JNDI name to
lookup the JMS connection factory from
(/ConnectionFactory by default in JBoss
AS) |
hibernate.search.<indexName>.worker.jms.queue | Mandatory for the JMS back end. Defines the JNDI name to lookup the JMS queue from. The queue will be used to post work messages. |
hibernate.search.<indexName>.worker.jms.login | Optional for the JMS slaves. Use it when your queue requires login credentials to define your login. |
hibernate.search.<indexName>.worker.jms.login | Optional for the JMS slaves. Use it when your queue requires login credentials to define your password. |
As you probably noticed, some of the shown properties are
correlated which means that not all combinations of property values make
sense. In fact you can end up with a non-functional configuration. This
is especially true for the case that you provide your own
implementations of some of the shown interfaces. Make sure to study the
existing code before you write your own Worker
or
BackendQueueProcessor
implementation.
This section describes in greater detail how to configure the Master/Slave Hibernate Search architecture.
Every index update operation is sent to a JMS queue. Index querying operations are executed on a local index copy.
Example 3.4. JMS Slave configuration
### slave configuration ## DirectoryProvider # (remote) master location hibernate.search.default.sourceBase = /mnt/mastervolume/lucenedirs/mastercopy # local copy location hibernate.search.default.indexBase = /Users/prod/lucenedirs # refresh every half hour hibernate.search.default.refresh = 1800 # appropriate directory provider hibernate.search.default.directory_provider = filesystem-slave ## Backend configuration hibernate.search.default.worker.backend = jms hibernate.search.default.worker.jms.connection_factory = /ConnectionFactory hibernate.search.default.worker.jms.queue = queue/hibernatesearch #optionally authentication credentials: hibernate.search.default.worker.jms.login = myname hibernate.search.default.worker.jms.password = wonttellyou #optional jndi configuration (check your JMS provider for more information) ## Optional asynchronous execution strategy # hibernate.search.default.worker.execution = async # hibernate.search.default.worker.thread_pool.size = 2 # hibernate.search.default.worker.buffer_queue.max = 50
A file system local copy is recommended for faster search results.
Every index update operation is taken from a JMS queue and executed. The master index is copied on a regular basis.
Example 3.5. JMS Master configuration
### master configuration ## DirectoryProvider # (remote) master location where information is copied to hibernate.search.default.sourceBase = /mnt/mastervolume/lucenedirs/mastercopy # local master location hibernate.search.default.indexBase = /Users/prod/lucenedirs # refresh every half hour hibernate.search.default.refresh = 1800 # appropriate directory provider hibernate.search.default.directory_provider = filesystem-master ## Backend configuration #Backend is the default lucene one
It is recommended that the refresh period be higher than the expected copy time; if a copy operation is still being performed when the next refresh triggers, the second refresh is skipped: it's safe to set this value low even when the copy time is not known.
In addition to the Hibernate Search framework configuration, a Message Driven Bean has to be written and set up to process the index works queue through JMS.
Example 3.6. Message Driven Bean processing the indexing queue
@MessageDriven(activationConfig = {
@ActivationConfigProperty(propertyName="destinationType",
propertyValue="javax.jms.Queue"),
@ActivationConfigProperty(propertyName="destination",
propertyValue="queue/hibernatesearch"),
@ActivationConfigProperty(propertyName="DLQMaxResent", propertyValue="1")
} )
public class MDBSearchController extends AbstractJMSHibernateSearchController
implements MessageListener {
@PersistenceContext EntityManager em;
//method retrieving the appropriate session
protected Session getSession() {
return (Session) em.getDelegate();
}
//potentially close the session opened in #getSession(), not needed here
protected void cleanSessionIfNeeded(Session session)
}
}
This example inherits from the abstract JMS controller class
available in the Hibernate Search source code and implements a JavaEE
MDB. This implementation is given as an example and can be adjusted to
make use of non Java EE Message Driven Beans. For more information
about the getSession()
and
cleanSessionIfNeeded()
, please check
AbstractJMSHibernateSearchController
's
javadoc.
This section describes how to configure the JGroups Master/Slave
back end. The master and slave roles are similar to what is illustrated
in Section 3.4.1, “JMS Master/Slave back end”, only a different backend
(hibernate.search.default.worker.backend
) needs to be
set.
A specific backend can be configured to act either as a slave
using jgroupsSlave
, as a master using
jgroupsMaster
, or can automatically switch between
the roles as needed by using jgroups
.
Either you specify a single jgroupsMaster
and
a set of jgroupsSlave
instances, or you specify all
instances as jgroups
. Never mix the two
approaches!
All backends configured to use JGroups share the same channel. The
JGroups JChannel
is the main communication link
across all nodes participating in the same cluster group; since it is
convenient to have just one channel shared across all backends, the
Channel configuration properties are not defined on a per-worker section
but are defined globally. See Section 3.4.2.4, “JGroups channel configuration”.
Table Table 3.6, “JGroups backend configuration properties”
contains all configuration options which can be set independently on
each index backend. These apply to all three variants of the backend:
jgroupsSlave
, jgroupsMaster
,
jgroups
. It is very unlikely that you need to change
any of these from their defaults.
Table 3.6. JGroups backend configuration properties
Property | Description |
hibernate.search.<indexName>.jgroups.block_waiting_ack | Set to either true or
false . False is more efficient but will not
wait for the operation to be delivered to the peers. Defaults to
true when the backend is synchronous, to
false when the backend is
async . |
hibernate.search.<indexName>.jgroups.messages_timeout | The timeout of waiting for a single command to be
acknowledged and executed when
block_waiting_ack is true ,
or just acknowledged otherwise. Value in milliseconds, defaults
to 20000 . |
hibernate.search.<indexName>.jgroups.delegate_backend | The master node receiving indexing operations forwards
them to a standard backend to be performed. Defaults to
lucene . See also Table 3.4, “Backend configuration” for other options, but
probably the only useful option is blackhole ,
or a custom implementation, to help isolating network latency
problems. |
Every index update operation is sent through a JGroups channel
to the master node. Index querying operations are executed on a local
index copy. Enabling the JGroups worker only makes sure the index
operations are sent to the master, you still have to synchronize
configuring an appropriate directory (See
filesystem-master
,
filesystem-slave
or infinispan
options in Section 3.3, “Directory configuration”).
Example 3.7. JGroups Slave configuration
### slave configuration hibernate.search.default.worker.backend = jgroupsSlave
Every index update operation is taken from a JGroups channel and executed. The master index is copied on a regular basis.
Example 3.8. JGroups Master configuration
### master configuration hibernate.search.default.worker.backend = jgroupsMaster
This feature is considered experimental. In particular during a re-election process there is a small window of time in which indexing requests could be lost.
In this mode the different nodes will autonomously elect a master node. When a master fails, a new node is elected automatically.
When setting this backend it is expected that all Hibernate
Search instances in the same cluster use the same backend for each
specific index: this configuration is an alternative to the static
jgroupsMaster
and jgroupsSlave
approach so make sure to not mix them.
To synchronize the indexes in this configuration avoid
filesystem-master
and
filesystem-slave
directory providers as their
behaviour can not be switched dynamically; use the Infinispan
Directory
instead, which has no need for different
configurations on each instance and allows dynamic switching of
writers; see also Section 3.3.1, “Infinispan Directory configuration”.
Example 3.9. JGroups configuration for automatic master configuration
### automatic configuration hibernate.search.default.worker.backend = jgroups
Should you use jgroups
or the couple
jgroupsMaster
,
jgroupsSlave
?
The dynamic jgroups
backend is better
suited for environments in which your master is more likely to need
to failover to a different machine, as in clouds. The static
configuration has the benefit of keeping the master at a well known
location: your architecture might take advantage of it by sending
most write requests to the known master. Also optimisation and
MassIndexer operations need to be triggered on the master
node.
Configuring the JGroups channel essentially entails specifying
the transport in terms of a network protocol stack. To configure the
JGroups transport, point the configuration property
hibernate.search.services.jgroups.configurationFile
to a JGroups configuration file; this can be either a file path or a
Java resource name.
If no property is explicitly specified it is assumed that the
JGroups default configuration file flush-udp.xml
is used. This example configuration is known to work in most
scenarios, with the notable exception of Amazon AWS; refer to the
JGroups
manual for more examples and protocol configuration
details.
The default cluster name is Hibernate Search
Cluster
which can be configured as seen in Example 3.10, “JGroups cluster name configuration”.
Example 3.10. JGroups cluster name configuration
hibernate.search.services.jgroups.clusterName = My-Custom-Cluster-Id
The cluster name is what identifies a group: by changing the name you can run different clusters in the same network in isolation.
For programmatic configurations, one additional option is
available to configure the JGroups channel: to pass an existing
channel instance to Hibernate Search directly using the property
hibernate.search.services.jgroups.providedChannel
,
as shown in the following example.
import org.hibernate.search.backend.impl.jgroups.JGroupsChannelProvider;
org.jgroups.JChannel channel = ...
Map<String,String> properties = new HashMap<String,String)(1);
properties.put( JGroupsChannelProvider.CHANNEL_INJECT, channel );
EntityManagerFactory emf = Persistence.createEntityManagerFactory( "userPU", properties );
The different reader strategies are described in Reader strategy. Out of the box strategies are:
shared
: share index readers across several
queries. This strategy is the most efficient.
not-shared
: create an index reader for each
individual query
The default reader strategy is shared
. This can
be adjusted:
hibernate.search.[default|<indexname>].reader.strategy = not-shared
Adding this property switches to the not-shared
strategy.
Or if you have a custom reader strategy:
hibernate.search.[default|<indexname>].reader.strategy = my.corp.myapp.CustomReaderProvider
where my.corp.myapp.CustomReaderProvider
is
the custom strategy implementation.
Hibernate Search allows you to configure how exceptions are handled during the indexing process. If no configuration is provided then exceptions are logged to the log output by default. It is possible to explicitly declare the exception logging mechanism as seen below:
hibernate.search.error_handler = log
The default exception handling occurs for both synchronous and asynchronous indexing. Hibernate Search provides an easy mechanism to override the default error handling implementation.
In order to provide your own implementation you must implement the
ErrorHandler
interface, which provides the
handle(ErrorContext context)
method.
ErrorContext
provides a reference to the primary
LuceneWork
instance, the underlying exception and any
subsequent LuceneWork
instances that could not be processed
due to the primary exception.
public interface ErrorContext {
List<LuceneWork> getFailingOperations();
LuceneWork getOperationAtFault();
Throwable getThrowable();
boolean hasErrors();
}
To register this error handler with Hibernate Search you must
declare the fully qualified classname of your
ErrorHandler
implementation in the configuration
properties:
hibernate.search.error_handler = CustomerErrorHandler
Even though Hibernate Search will try to shield you as much as possible from Lucene specifics, there are several Lucene specifics which can be directly configured, either for performance reasons or for satisfying a specific usecase. The following sections discuss these configuration options.
Hibernate Search allows you to tune the Lucene indexing
performance by specifying a set of parameters which are passed through
to underlying Lucene IndexWriter
such as
mergeFactor
, maxMergeDocs
and
maxBufferedDocs
. You can specify these parameters
either as default values applying for all indexes, on a per index basis,
or even per shard.
There are several low level IndexWriter
settings which can be tuned for different use cases. These parameters
are grouped by the indexwriter
keyword:
hibernate.search.[default|<indexname>].indexwriter.<parameter_name>
If no value is set for an indexwriter
value in
a specific shard configuration, Hibernate Search will look at the index
section, then at the default section.
Example 3.11. Example performance option configuration
hibernate.search.Animals.2.indexwriter.max_merge_docs = 10 hibernate.search.Animals.2.indexwriter.merge_factor = 20 hibernate.search.Animals.2.indexwriter.term_index_interval = default hibernate.search.default.indexwriter.max_merge_docs = 100 hibernate.search.default.indexwriter.ram_buffer_size = 64
The configuration in Example 3.11, “Example performance option configuration” will result in
these settings applied on the second shard of the
Animal
index:
max_merge_docs
= 10
merge_factor
= 20
ram_buffer_size
= 64MB
term_index_interval
= Lucene default
All other values will use the defaults defined in Lucene.
The default for all values is to leave them at Lucene's own
default. The values listed in Table 3.7, “List of indexing performance and behavior properties” depend for this reason on the
version of Lucene you are using. The values shown are relative to
version 2.4
. For more information about Lucene
indexing performance, please refer to the Lucene documentation.
Table 3.7. List of indexing performance and behavior properties
Property | Description | Default Value |
---|---|---|
hibernate.search.[default|<indexname>].exclusive_index_use |
Set to | true (improved performance, releases
locks only at shutdown) |
hibernate.search.[default|<indexname>].max_queue_length |
Each index has a separate "pipeline" which contains the
updates to be applied to the index. When this queue is full
adding more operations to the queue becomes a blocking
operation. Configuring this setting doesn't make much sense
unless the |
1000
|
hibernate.search.[default|<indexname>].indexwriter.max_buffered_delete_terms |
Determines the minimal number of delete terms required before the buffered in-memory delete terms are applied and flushed. If there are documents buffered in memory at the time, they are merged and a new segment is created. | Disabled (flushes by RAM usage) |
hibernate.search.[default|<indexname>].index_flush_interval |
The interval in milliseconds between flushes of write operations
to the index storage. Ignored unless |
1000
|
hibernate.search.[default|<indexname>].indexwriter.max_buffered_docs |
Controls the amount of documents buffered in memory during indexing. The bigger the more RAM is consumed. | Disabled (flushes by RAM usage) |
hibernate.search.[default|<indexname>].indexwriter.max_merge_docs |
Defines the largest number of documents allowed in a segment. Smaller values perform better on frequently changing indexes, larger values provide better search performance if the index does not change often. | Unlimited (Integer.MAX_VALUE) |
hibernate.search.[default|<indexname>].indexwriter.merge_factor |
Controls segment merge frequency and size. Determines how often segment indexes are merged when insertion occurs. With smaller values, less RAM is used while indexing, and searches on unoptimized indexes are faster, but indexing speed is slower. With larger values, more RAM is used during indexing, and while searches on unoptimized indexes are slower, indexing is faster. Thus larger values (> 10) are best for batch index creation, and smaller values (< 10) for indexes that are interactively maintained. The value must not be lower than 2. | 10 |
hibernate.search.[default|<indexname>].indexwriter.merge_min_size |
Controls segment merge frequency and size. Segments smaller than this size (in MB) are always considered for the next segment merge operation. Setting this too large might result in expensive merge operations, even tough they are less frequent. See also
| 0 MB (actually ~1K) |
hibernate.search.[default|<indexname>].indexwriter.merge_max_size |
Controls segment merge frequency and size. Segments larger than this size (in MB) are never merged in bigger segments. This helps reduce memory requirements and avoids some merging operations at the cost of optimal search speed. When optimizing an index this value is ignored. See also
| Unlimited |
hibernate.search.[default|<indexname>].indexwriter.merge_max_optimize_size |
Controls segment merge frequency and size. Segments larger than this size (in MB) are not merged in
bigger segments even when optimizing the index (see
Applied to
| Unlimited |
hibernate.search.[default|<indexname>].indexwriter.merge_calibrate_by_deletes |
Controls segment merge frequency and size. Set to Applied to
|
true
|
hibernate.search.[default|<indexname>].indexwriter.ram_buffer_size |
Controls the amount of RAM in MB dedicated to document buffers. When used together max_buffered_docs a flush occurs for whichever event happens first. Generally for faster indexing performance it's best to flush by RAM usage instead of document count and use as large a RAM buffer as you can. | 16 MB |
hibernate.search.[default|<indexname>].indexwriter.term_index_interval |
Expert: Set the interval between indexed terms. Large values cause less memory to be used by IndexReader, but slow random-access to terms. Small values cause more memory to be used by an IndexReader, and speed random-access to terms. See Lucene documentation for more details. | 128 |
hibernate.search.[default|<indexname>].indexwriter.use_compound_file | The advantage of using the compound file format is that
less file descriptors are used. The disadvantage is that
indexing takes more time and temporary disk space. You can set
this parameter to false in an attempt to
improve the indexing time, but you could run out of file
descriptors if mergeFactor is also
large.Boolean parameter, use " | true |
hibernate.search.enable_dirty_check |
Not all entity changes require an update of the Lucene index. If all of the updated entity properties (dirty properties) are not indexed Hibernate Search will skip the re-indexing work. Disable this option if you use custom
This optimization will not be applied on classes using a
Boolean parameter, use " | true |
When your architecture permits it, always keep
hibernate.search.default.exclusive_index_use=true
as it greatly improves efficiency in index writing. This is the
default since Hibernate Search version 4.
To tune the indexing speed it might be useful to time the object
loading from database in isolation from the writes to the index. To
achieve this set the blackhole
as worker backend
and start your indexing routines. This backend does not disable
Hibernate Search: it will still generate the needed changesets to the
index, but will discard them instead of flushing them to the index. In
contrast to setting the
hibernate.search.indexing_strategy
to
manual
, using blackhole
will
possibly load more data from the database. because associated entities
are re-indexed as well.
hibernate.search.[default|<indexname>].worker.backend blackhole
The recommended approach is to focus first on optimizing the object loading, and then use the timings you achieve as a baseline to tune the indexing process.
The blackhole
backend is not meant to be used
in production, only as a tool to identify indexing bottlenecks.
The options merge_max_size
,
merge_max_optimize_size
,
merge_calibrate_by_deletes
give you control on the
maximum size of the segments being created, but you need to understand
how they affect file sizes. If you need to hard limit the size,
consider that merging a segment is about adding it together with
another existing segment to form a larger one, so you might want to
set the max_size
for merge operations to less than
half of your hard limit. Also segments might initially be generated
larger than your expected size at first creation time: before they are
ever merged. A segment is never created much larger than
ram_buffer_size
, but the threshold is checked as an
estimate.
Example:
//to be fairly confident no files grow above 15MB, use: hibernate.search.default.indexwriter.ram_buffer_size = 10 hibernate.search.default.indexwriter.merge_max_optimize_size = 7 hibernate.search.default.indexwriter.merge_max_size = 7
When using the Infinispan Directory to cluster indexes make sure
that your segments are smaller than the chunk_size
so that you avoid fragmenting segments in the grid. Note that the
chunk_size
of the Infinispan Directory is expressed
in bytes, while the index tuning options are in MB.
Lucene Directory
s have default locking
strategies which work generally good enough for most cases, but it's
possible to specify for each index managed by Hibernate Search a
specific LockingFactory
you want to use. This is
generally not needed but could be useful.
Some of these locking strategies require a filesystem level lock
and may be used even on RAM based indexes, this combination is valid but
in this case the indexBase
configuration option
usually needed only for filesystem based
Directory
instances must be specified to point to
a filesystem location where to store the lock marker files.
To select a locking factory, set the
hibernate.search.<index>.locking_strategy
option to one of simple
, native
,
single
or none
. Alternatively set
it to the fully qualified name of an implementation of
org.hibernate.search.store.LockFactoryProvider
.
Table 3.8. List of available LockFactory implementations
name | Class | Description |
---|---|---|
simple | org.apache.lucene.store.SimpleFSLockFactory | Safe implementation based on Java's File API, it marks the usage of the index by creating a marker file. If for some reason you had to kill your application, you will need to remove this file before restarting it. |
native | org.apache.lucene.store.NativeFSLockFactory | As does This implementation has known problems on NFS, avoid it on network shares.
|
single | org.apache.lucene.store.SingleInstanceLockFactory | This LockFactory doesn't use a file marker but is a Java object lock held in memory; therefore it's possible to use it only when you are sure the index is not going to be shared by any other process. This is the default
implementation for the |
none | org.apache.lucene.store.NoLockFactory | All changes to this index are not coordinated by any lock; test your application carefully and make sure you know what it means. |
Configuration example:
hibernate.search.default.locking_strategy = simple hibernate.search.Animals.locking_strategy = native hibernate.search.Books.locking_strategy = org.custom.components.MyLockingFactory
The Infinispan Directory uses a custom implementation; it's still possible to override it but make sure you understand how that will work, especially with clustered indexes.
While Hibernate Search strives to offer a backwards compatible API making it easy to port your application to newer versions, it still delegates to Apache Lucene to handle the index writing and searching. This creates a dependency to the Lucene index format. The Lucene developers of course attempt to keep a stable index format, but sometimes a change in the format can not be avoided. In those cases you either have to reindex all your data or use an index upgrade tool. Sometimes Lucene is also able to read the old format so you don't need to take specific actions (besides making backup of your index).
While an index format incompatibility is a rare event, it can
happen more often that Lucene's Analyzer
implementations might slightly change its behaviour. This can lead to a
poor recall score, possibly missing many hits from the results.
Hibernate Search exposes a configuration property
hibernate.search.lucene_version
which instructs the
analyzers and other Lucene classes to conform to their behaviour as
defined in an (older) specific version of Lucene. See also
org.apache.lucene.util.Version
contained in the
lucene-core.jar
. Depending on the specific version
of Lucene you're using you might have different options available. When
this option is not specified, Hibernate Search will instruct Lucene to
use the default version, which is usually the best option for new
projects. Still it's recommended to define the version you're using
explicitly in the configuration so that when you happen to upgrade
Lucene the analyzers will not change behaviour. You can then choose to
update this value at a later time, when you for example have the chance
to rebuild the index from scratch.
Example 3.12. Force Analyzers to be compatible with a Lucene 3.0 created index
hibernate.search.lucene_version = LUCENE_30
This option is global for the configured
SearchFactory
and affects all Lucene APIs having
such a parameter, as this should be applied consistently. So if you are
also making use of Lucene bypassing Hibernate Search, make sure to apply
the same value too.
After looking at all these different configuration options, it is
time to have a look at an API which allows you to prorgammatically access
parts of the configuration. Via the metadata API you can determine the
indexed types and also how they are mapped (see Chapter 4, Mapping entities to the index structure) to the index structure. The entry point into
this API is the SearchFactory
. It offers two
methods, namely getIndexedTypes()
and
getIndexedTypeDescriptor(Class<?>)
. The
former returns a set of all indexed type, where as the latter allows to
retrieve a so called IndexedTypeDescriptor
for a
gven type. This descriptor allows you determine whether the type is
indexed at all and, if so, whether the index is for example sharded or not
(see Section 10.4, “Sharding indexes”). It also
allows you to determine the static boost of the type (see Section 4.2.1, “Static index time boosting”) as well as its dynamic boost
strategy (see Section 4.2.2, “Dynamic index time boosting”). Most importantly,
however, you get information about the indexed properties and generated
Lucene Document
fields. This is exposed via
PropertyDescriptor
s respectively
FieldDescriptor
s. The easiest way to get to know
the API is to explore it via the IDE or its javadocs.
All descriptor instances of the metadata API are read only. They do not allow to change any runtime configuration.
Provided you're deploying on JBoss AS 7.x or JBoss EAP 6.x, there is an additional way to add the search dependencies to your application.
In JBoss AS 7 class loading is based on modules that have to define explicit dependencies on other modules. Modules allow to share the same artifacts across multiple applications getting you smaller and quicker deployments.
More details about modules are described in Class Loading in AS7.
You can download the pre-packaged Hibernate Search modules from:
Unpack the modules in your JBoss AS modules
directory: this will create modules for Hibernate Search, Apache Lucene
and some useful Solr libraries. The Hibernate Search modules are:
org.hibernate.search.orm:main, for users of Hibernate Search with Hibernate; this will transitively include Hibernate ORM.
org.hibernate.search.engine:main, for projects depending on the internal indexing engine that don't require other dependencies to Hibernate.
There are two ways to include the dependencies in your project:
Add this entry to the MANIFEST.MF in your archive:
Dependencies: org.hibernate.search.orm services
This is a proprietary JBoss AS descriptor, add a WEB-INF/jboss-deployment-structure.xml in your archive with content:
<jboss-deployment-structure>
<deployment>
<dependencies>
<module name="org.hibernate.search.orm" services="export" />
</dependencies>
</deployment>
</jboss-deployment-structure>
More information about the descriptor can be found in the JBoss AS 7 documentation.
Modular classloading is a feature of JBoss EAP as well, but if you are using JBoss EAP, you're reading the wrong version of the user guide! JBoss EAP subscriptions include official support for Hibernate Search (as part of the WFK) and come with a different edition of this guide specifically tailored for EAP users.
In Chapter 1, Getting started you have already learned that all the metadata information needed to index entities is described through annotations. There is no need for xml mapping files. You can still use Hibernate mapping files for the basic Hibernate configuration, but the Hibernate Search specific configuration has to be expressed via annotations.
There is no XML configuration available for Hibernate Search but we provide a powerful programmatic mapping API that elegantly replaces this kind of deployment form (see Section 4.7, “Programmatic API” for more information).
If you want to contribute the XML mapping implementation, see HSEARCH-210.
Lets start with the most commonly used annotations when mapping an entity.
Foremost you must declare a persistent class as indexable by
annotating the class with @Indexed.
All entities
not annotated with @Indexed
will be ignored by the
indexing process.
You can optionally specify the
attribute to
change the default name of the index. For more information regarding
index naming see Section 3.3, “Directory configuration”.Indexed.index
You can also specify an optional indexing interceptor. For more information see Section 4.5, “Conditional indexing: to index or not based on entity state”.
For each property (or attribute) of your entity, you have the
ability to describe how it will be indexed. The default (no annotation
present) means that the property is ignored by the indexing process.
@Field
does declare a property as indexed and
allows you to configure several aspects of the indexing process by
setting one or more of the following attributes:
name
: describe under which name the
property should be stored in the Lucene Document. The default
value is the property name (following the JavaBeans
convention)
store
: describe whether or not the
property is stored in the Lucene index. You can store the value
Store.YES
(consuming more space in the index
but allowing projection, see Section 5.1.3.5, “Projection”), store
it in a compressed way Store.COMPRESS
(this
does consume more CPU), or avoid any storage
Store.NO
(this is the default value). When a
property is stored, you can retrieve its original value from the
Lucene Document. Storing the property has no impact though on
whether the value is searchable or not.
index
: describe whether the property is
indexed or not. The different values are
Index.NO
(no indexing, i.e. cannot be found by
a query), Index.YES
(the element gets indexed
and is searchable). The default value is
Index.YES
. Index.NO
can be
useful for cases where a property is not required to be
searchable, but should be available for projection.
Index.NO
in combination with
Analyze.YES
or Norms.YES
is not useful, since analyze
and
norms
require the property to be
indexed
analyze
: determines whether the property
is analyzed (Analyze.YES
) or not
(Analyze.NO
). The default value is
Analyze.YES
.
Whether or not you want to analyze a property depends on whether you wish to search the element as is, or by the words it contains. It make sense to analyze a text field, but probably not a date field.
Fields used for sorting or faceting must not be analyzed.
norms
: describes whether index time
boosting information should be stored
(Norms.YES
) or not
(Norms.NO
). Not storing the norms can save a
considerable amount of memory, but index time boosting will not be
available in this case. The default value is
Norms.YES
.
termVector
: describes collections of
term-frequency pairs. This attribute enables the storing of the
term vectors within the documents during indexing. The default
value is TermVector.NO
.
The different values of this attribute are:
Value | Definition |
---|---|
TermVector.YES | Store the term vectors of each document. This produces two synchronized arrays, one contains document terms and the other contains the term's frequency. |
TermVector.NO | Do not store term vectors. |
TermVector.WITH_OFFSETS | Store the term vector and token offset information. This is the same as TermVector.YES plus it contains the starting and ending offset position information for the terms. |
TermVector.WITH_POSITIONS | Store the term vector and token position information. This is the same as TermVector.YES plus it contains the ordinal positions of each occurrence of a term in a document. |
TermVector.WITH_POSITION_OFFSETS | Store the term vector, token position and offset information. This is a combination of the YES, WITH_OFFSETS and WITH_POSITIONS. |
indexNullAs
: Per default
null
values are ignored and not indexed.
However, using indexNullAs
you can specify
a string which will be inserted as token for the
null
value. Per default this value is set to
org.hibernate.search.annotations.Field.DO_NOT_INDEX_NULL
indicating that null
values should not be
indexed. You can set this value to DEFAULT_NULL_TOKEN
to indicate that a default null
token should be used. This default null
token
can be specified in the configuration using
hibernate.search.default_null_token
. If this
property is not set the string "_null_" will be used as default.
When indexNullAs
is used, it is
important to use the chosen null
token in
search queries (see Querying) in order
to find null
values. It is also advisable
to use this feature only with un-analyzed fields
(
).analyze=
Analyze.NO
When implementing a custom
FieldBridge
or
TwoWayFieldBridge
it is up to the
developer to handle the indexing of null values (see JavaDocs
of
LuceneOptions.indexNullAs()
).
There exists also a companion annotation to
@Field,
called
@NumericField.
It can be specified in the same
scope as @Field
or
@DocumentId
, but only on
Integer
, Long
,
Float
or Double
properties. When used, the annoated property will be indexed using a
Trie structure.
This enables efficient range queries and sorting, resulting in query
response times being orders of magnitude faster than the same query
with plain @Field
. The
@NumericField
annotation accepts the following
parameters:
Value | Definition |
---|---|
forField | (Optional) Specify the name of of the related @Field that will be indexed as numeric. It's only mandatory when the property contains more than a @Field declaration |
precisionStep | (Optional) Change the way that the Trie structure is stored in the index. Smaller precisionSteps lead to more disk space usage and faster range and sort queries. Larger values lead to less space used and range query performance more close to the range query in normal @Fields. Default value is 4. |
Lucene supports the numeric types: Double, Long,
Integer and Float. Other numeric types should use the default string
encoding (via @Field
), unless the application
can deal with a potential loss in precision, in which case a custom
NumericFieldBridge
can be used. See Example 4.2, “Defining a custom NumericFieldBridge for
BigDecimal
”.
Example 4.2. Defining a custom NumericFieldBridge for
BigDecimal
public class BigDecimalNumericFieldBridge extends NumericFieldBridge {
private static final BigDecimal storeFactor = BigDecimal.valueOf(100);
@Override
public void set(String name, Object value, Document document, LuceneOptions luceneOptions) {
if ( value != null ) {
BigDecimal decimalValue = (BigDecimal) value;
Long indexedValue = Long.valueOf( decimalValue.multiply( storeFactor ).longValue() );
luceneOptions.addNumericFieldToDocument( name, indexedValue, document );
}
}
@Override
public Object get(String name, Document document) {
String fromLucene = document.get( name );
BigDecimal storedBigDecimal = new BigDecimal( fromLucene );
return storedBigDecimal.divide( storeFactor );
}
}
You would use this custom bridge like seen in Example 4.3, “Use of BigDecimalNumericFieldBridge”. In this case
three annotations are used - @Field
,
@NumericField
and
@FieldBridge
. @Field
is
required to mark the property for being indexed (a standalone
@NumericField
is never allowed).
@NumericField
might be ommited in this specific
case, because the used @FieldBridge
annotation
refers already to a NumericFieldBridge
instance. However, the use of @NumericField
is
recommended to make the use of the property as numeric value
explicit.
Example 4.3. Use of BigDecimalNumericFieldBridge
@Entity
@Indexed
public static class Item {
@Id
@GeneratedValue
private int id;
@Field
@NumericField
@FieldBridge(impl = BigDecimalNumericFieldBridge.class)
private BigDecimal price;
public int getId() {
return id;
}
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
}
Finally, the id property of an entity is a special property used
by Hibernate Search to ensure index unicity of a given entity. By
design, an id has to be stored and must not be tokenized. To mark a
property as index id, use the @DocumentId
annotation. If you are using JPA and you have specified
@Id
you can omit
@DocumentId
. The chosen entity id will also be
used as document id.
Example 4.4. Specifying indexed properties
@Entity
@Indexed
public class Essay {
...
@Id
@DocumentId
public Long getId() { return id; }
@Field(name="Abstract", store=Store.YES)
public String getSummary() { return summary; }
@Lob
@Field
public String getText() { return text; }
@Field @NumericField(precisionStep = 6)
public float getGrade() { return grade; }
}
Example 4.4, “Specifying indexed properties” defines an index with
four fields: id
, Abstract
,
text
and grade
. Note that by
default the field name is decapitalized, following the JavaBean
specification. The grade
field is annotated as
Numeric with a slightly larger precisionStep than the default.
Sometimes one has to map a property multiple times per index, with slightly different indexing strategies. For example, sorting a query by field requires the field to be un-analyzed. If one wants to search by words in this property and still sort it, one need to index it twice - once analyzed and once un-analyzed. @Fields allows to achieve this goal.
Example 4.5. Using @Fields to map a property multiple times
@Entity
@Indexed(index = "Book")
public class Book {
@Fields( {
@Field,
@Field(name = "summary_forSort", analyze = Analyze.NO, store = Store.YES)
} )
public String getSummary() {
return summary;
}
...
}
In Example 4.5, “Using @Fields to map a property multiple times” the field
summary
is indexed twice, once as
summary
in a tokenized way, and once as
summary_forSort
in an untokenized way. @Field
supports 2 attributes useful when @Fields is used:
analyzer: defines a @Analyzer annotation per field rather than per property
bridge: defines a @FieldBridge annotation per field rather than per property
See below for more information about analyzers and field bridges.
Associated objects as well as embedded objects can be indexed as
part of the root entity index. This is useful if you expect to search a
given entity based on properties of associated objects. In Example 4.6, “Indexing associations”t the aim is to return places
where the associated city is Atlanta (In the Lucene query parser
language, it would translate into address.city:Atlanta
).
The place fields will be indexed in the Place
index.
The Place
index documents will also contain the
fields address.id
, address.street
,
and address.city
which you will be able to
query.
Example 4.6. Indexing associations
@Entity
@Indexed
public class Place {
@Id
@GeneratedValue
@DocumentId
private Long id;
@Field
private String name;
@OneToOne(cascade = { CascadeType.PERSIST, CascadeType.REMOVE })
@IndexedEmbedded
private Address address;
....
}
@Entity
public class Address {
@Id
@GeneratedValue
private Long id;
@Field
private String street;
@Field
private String city;
@ContainedIn
@OneToMany(mappedBy="address")
private Set<Place> places;
...
}
Be careful. Because the data is denormalized in the Lucene index
when using the @IndexedEmbedded
technique,
Hibernate Search needs to be aware of any change in the
Place
object and any change in the
Address
object to keep the index up to date. To
make sure the
Lucene
document is updated when it's Place
Address
changes,
you need to mark the other side of the bidirectional relationship with
@ContainedIn
.
@ContainedIn
is useful on both associations
pointing to entities and on embedded (collection of) objects.
Let's make Example 4.6, “Indexing associations” a bit
more complex by nesting @IndexedEmbedded as seen in Example 4.7, “Nested usage of @IndexedEmbedded
and
@ContainedIn
”.
Example 4.7. Nested usage of @IndexedEmbedded
and
@ContainedIn
@Entity
@Indexed
public class Place {
@Id
@GeneratedValue
@DocumentId
private Long id;
@Field
private String name;
@OneToOne(cascade = { CascadeType.PERSIST, CascadeType.REMOVE })
@IndexedEmbedded
private Address address;
....
}
@Entity
public class Address {
@Id
@GeneratedValue
private Long id;
@Field
private String street;
@Field
private String city;
@IndexedEmbedded(depth = 1, prefix = "ownedBy_")
private Owner ownedBy;
@ContainedIn
@OneToMany(mappedBy="address")
private Set<Place> places;
...
}
@Embeddable
public class Owner {
@Field
private String name;
...
}
As you can see, any @*ToMany, @*ToOne
and
@Embedded
attribute can be annotated with
@IndexedEmbedded
. The attributes of the associated
class will then be added to the main entity index. In Example 4.7, “Nested usage of @IndexedEmbedded
and
@ContainedIn
” the index will contain the
following fields
id
name
address.street
address.city
address.ownedBy_name
The default prefix is propertyName.
, following
the traditional object navigation convention. You can override it using
the prefix
attribute as it is shown on the
ownedBy
property.
The prefix cannot be set to the empty string.
The depth
property is necessary when the object
graph contains a cyclic dependency of classes (not instances). For
example, if Owner
points to
Place
. Hibernate Search will stop including
Indexed embedded attributes after reaching the expected depth (or the
object graph boundaries are reached). A class having a self reference is
an example of cyclic dependency. In our example, because
depth
is set to 1, any
@IndexedEmbedded
attribute in Owner (if any) will be
ignored.
Using @IndexedEmbedded
for object associations
allows you to express queries (using Lucene's query syntax) such
as:
Return places where name contains JBoss and where address city is Atlanta. In Lucene query this would be
+name:jboss +address.city:atlanta
Return places where name contains JBoss and where owner's name contain Joe. In Lucene query this would be
+name:jboss +address.ownedBy_name:joe
In a way it mimics the relational join operation in a more efficient way (at the cost of data duplication). Remember that, out of the box, Lucene indexes have no notion of association, the join operation is simply non-existent. It might help to keep the relational model normalized while benefiting from the full text index speed and feature richness.
An associated object can itself (but does not have to) be
@Indexed
When @IndexedEmbedded points to an entity, the association has to
be directional and the other side has to be annotated
@ContainedIn
(as seen in the previous example). If
not, Hibernate Search has no way to update the root index when the
associated entity is updated (in our example, a Place
index document has to be updated when the associated
Address
instance is updated).
Sometimes, the object type annotated by
@IndexedEmbedded
is not the object type targeted
by Hibernate and Hibernate Search. This is especially the case when
interfaces are used in lieu of their implementation. For this reason you
can override the object type targeted by Hibernate Search using the
targetElement
parameter.
Example 4.8. Using the targetElement
property of
@IndexedEmbedded
@Entity
@Indexed
public class Address {
@Id
@GeneratedValue
@DocumentId
private Long id;
@Field
private String street;
@IndexedEmbedded(depth = 1, prefix = "ownedBy_", targetElement = Owner.class)
@Target(Owner.class)
private Person ownedBy;
...
}
@Embeddable
public class Owner implements Person { ... }
The @IndexedEmbedded
annotation provides
also an attribute includePaths
which can be
used as an alternative to depth
, or be
combined with it.
When using only depth
all indexed
fields of the embedded type will be added recursively at the same
depth; this makes it harder to pick only a specific path without
adding all other fields as well, which might not be needed.
To avoid unnecessarily loading and indexing entities you can
specify exactly which paths are needed. A typical application might
need different depths for different paths, or in other words it might
need to specify paths explicitly, as shown in Example 4.9, “Using the includePaths
property of
@IndexedEmbedded
”
Example 4.9. Using the includePaths
property of
@IndexedEmbedded
@Entity
@Indexed
public class Person {
@Id
public int getId() {
return id;
}
@Field
public String getName() {
return name;
}
@Field
public String getSurname() {
return surname;
}
@OneToMany
@IndexedEmbedded(includePaths = { "name" })
public Set<Person> getParents() {
return parents;
}
@ContainedIn
@ManyToOne
public Human getChild() {
return child;
}
...//other fields omitted
Using a mapping as in Example 4.9, “Using the includePaths
property of
@IndexedEmbedded
”, you would be able to search
on a Person
by name
and/or
surname
, and/or the name
of the
parent. It will not index the surname
of the
parent, so searching on parent's surnames will not be possible but
speeds up indexing, saves space and improve overall
performance.
The @IndexedEmbedded
includePaths
will include the specified paths
in addition to what you would index normally
specifying a limited value for depth
. When
using includePaths
, and leaving
depth
undefined, behavior is equivalent to
setting depth
=0
: only the
included paths are indexed.
Example 4.10. Using the includePaths
property of
@IndexedEmbedded
@Entity
@Indexed
public class Human {
@Id
public int getId() {
return id;
}
@Field
public String getName() {
return name;
}
@Field
public String getSurname() {
return surname;
}
@OneToMany
@IndexedEmbedded(depth = 2, includePaths = { "parents.parents.name" })
public Set<Human> getParents() {
return parents;
}
@ContainedIn
@ManyToOne
public Human getChild() {
return child;
}
...//other fields omitted
In Example 4.10, “Using the includePaths
property of
@IndexedEmbedded
”, every
human will have it's name and surname attributes indexed. The name and
surname of parents will be indexed too, recursively up to second line
because of the depth
attribute. It will be
possible to search by name or surname, of the person directly, his
parents or of his grand parents. Beyond the second level, we will in
addition index one more level but only the name, not the
surname.
This results in the following fields in the index:
id
- as primary key
_hibernate_class
- stores entity
type
name
- as direct field
surname
- as direct field
parents.name
- as embedded field at depth
1
parents.surname
- as embedded field at
depth 1
parents.parents.name
- as embedded field
at depth 2
parents.parents.surname
- as embedded
field at depth 2
parents.parents.parents.name
- as
additional path as specifyed by
includePaths
. The first
parents.
is inferred from the field name, the
remaining path is the attribute of
includePaths
Having explicit control of the indexed paths might be easier if you're designing your application by defining the needed queries first, as at that point you might know exactly which fields you need, and which other fields are unnecessary to implement your use case.
Lucene has the notion of boosting which allows you to give certain documents or fields more or less importance than others. Lucene differentiates between index and search time boosting. The following sections show you how you can achieve index time boosting using Hibernate Search.
To define a static boost value for an indexed class or property
you can use the @Boost
annotation. You can use
this annotation within @Field or specify it directly on method or class
level.
Example 4.11. Different ways of using @Boost
@Entity @Indexed @Boost(1.7f) public class Essay { ... @Id @DocumentId public Long getId() { return id; } @Field(name="Abstract", store=Store.YES, boost=@Boost(2f)) @Boost(1.5f) public String getSummary() { return summary; } @Lob @Field(boost=@Boost(1.2f)) public String getText() { return text; } @Field public String getISBN() { return isbn; } }
In Example 4.11, “Different ways of using @Boost”, Essay
's
probability to reach the top of the search list will be multiplied by
1.7. The summary
field will be 3.0 (2 * 1.5,
because @Field.boost
and
@Boost
on a property are cumulative) more
important than the isbn
field. The
text
field will be 1.2 times more important
than the isbn
field. Note that this explanation
is wrong in strictest terms, but it is simple and close enough to
reality for all practical purposes. Please check the Lucene
documentation or the excellent Lucene In Action
from Otis Gospodnetic and Erik Hatcher.
The @Boost
annotation used in Section 4.2.1, “Static index time boosting” defines a static boost factor which
is independent of the state of of the indexed entity at runtime.
However, there are usecases in which the boost factor may depend on the
actual state of the entity. In this case you can use the
@DynamicBoost
annotation together with an
accompanying custom BoostStrategy
.
Example 4.12. Dynamic boost example
public enum PersonType {
NORMAL,
VIP
}
@Entity
@Indexed @DynamicBoost(impl = VIPBoostStrategy.class)
public class Person {
private PersonType type;
// ....
}
public class VIPBoostStrategy implements BoostStrategy {
public float defineBoost(Object value) {
Person person = ( Person ) value;
if ( person.getType().equals( PersonType.VIP ) ) {
return 2.0f;
}
else {
return 1.0f;
}
}
}
In Example 4.12, “Dynamic boost example” a dynamic boost is
defined on class level specifying
VIPBoostStrategy
as implementation of the
BoostStrategy
interface to be used at indexing
time. You can place the @DynamicBoost
either at class
or field level. Depending on the placement of the annotation either the
whole entity is passed to the defineBoost
method or just the annotated field/property value. It's up to you to
cast the passed object to the correct type. In the example all indexed
values of a VIP person would be double as important as the values of a
normal person.
The specified BoostStrategy
implementation must define a public no-arg constructor.
Of course you can mix and match @Boost
and
@DynamicBoost
annotations in your entity. All defined
boost factors are cumulative.
Analysis
is the process of converting text into
single terms (words) and can be considered as one of the key features of a
fulltext search engine. Lucene uses the concept of
Analyzer
s to control this process. In the following
section we cover the multiple ways Hibernate Search offers to configure
the analyzers.
The default analyzer class used to index tokenized fields is
configurable through the hibernate.search.analyzer
property. The default value for this property is
org.apache.lucene.analysis.standard.StandardAnalyzer
.
You can also define the analyzer class per entity, property and even per @Field (useful when multiple fields are indexed from a single property).
Example 4.13. Different ways of using @Analyzer
@Entity
@Indexed @Analyzer(impl = EntityAnalyzer.class)
public class MyEntity {
@Id
@GeneratedValue
@DocumentId
private Integer id;
@Field
private String name;
@Field
@Analyzer(impl = PropertyAnalyzer.class)
private String summary;
@Field(analyzer = @Analyzer(impl = FieldAnalyzer.class)
private String body;
...
}
In this example, EntityAnalyzer
is used to
index all tokenized properties (eg. name
), except
summary
and body
which are indexed
with PropertyAnalyzer
and
FieldAnalyzer
respectively.
Mixing different analyzers in the same entity is most of the time a bad practice. It makes query building more complex and results less predictable (for the novice), especially if you are using a QueryParser (which uses the same analyzer for the whole query). As a rule of thumb, for any given field the same analyzer should be used for indexing and querying.
Analyzers can become quite complex to deal with. For this reason
introduces Hibernate Search the notion of analyzer definitions. An
analyzer definition can be reused by many
@Analyzer
declarations and is composed of:
a name: the unique string used to refer to the definition
a list of char filters: each char filter is responsible to pre-process input characters before the tokenization. Char filters can add, change or remove characters; one common usage is for characters normalization
a tokenizer: responsible for tokenizing the input stream into individual words
a list of filters: each filter is responsible to remove, modify or sometimes even add words into the stream provided by the tokenizer
This separation of tasks - a list of char filters, and a tokenizer
followed by a list of filters - allows for easy reuse of each individual
component and let you build your customized analyzer in a very flexible
way (just like Lego). Generally speaking the char filters do some
pre-processing in the character input, then the
Tokenizer
starts the tokenizing process by
turning the character input into tokens which are then further processed
by the TokenFilter
s. Hibernate Search supports
this infrastructure by utilizing the Solr analyzer framework.
Some of the analyzers and filters will require additional
dependencies. For example to use the snowball stemmer you have to also
include the lucene-snowball
jar and for the
PhoneticFilterFactory
you need the commons-codec jar. Your
distribution of Hibernate Search provides these dependencies in its
lib/optional
directory. Have a look at Table 4.2, “Example of available tokenizers” and Table 4.3, “Examples of available filters” to see which anaylzers and filters
have additional dependencies
Prior to Search version 3.3.0.Beta2 it was required to add the Solr dependency org.apache.solr:solr-core when you wanted to use the analyzer definition framework. In case you are using Maven this is no longer needed: all required Solr dependencies are now defined as dependencies of the artifact org.hibernate:hibernate-search-analyzers; just add the following dependency :
<dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-search-analyzers</artifactId> <version>4.4.6.Final</version> <dependency>
Let's have a look at a concrete example now - Example 4.14, “@AnalyzerDef
and the Solr
framework”. First a char filter is defined by its
factory. In our example, a mapping char filter is used, and will replace
characters in the input based on the rules specified in the mapping
file. Next a tokenizer is defined. This example uses the standard
tokenizer. Last but not least, a list of filters is defined by their
factories. In our example, the StopFilter
filter
is built reading the dedicated words property file. The filter is also
expected to ignore case.
Example 4.14. @AnalyzerDef
and the Solr
framework
@AnalyzerDef(name="customanalyzer",
charFilters = {
@CharFilterDef(factory = MappingCharFilterFactory.class, params = {
@Parameter(name = "mapping",
value = "org/hibernate/search/test/analyzer/solr/mapping-chars.properties")
})
},
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = ISOLatin1AccentFilterFactory.class),
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = StopFilterFactory.class, params = {
@Parameter(name="words",
value= "org/hibernate/search/test/analyzer/solr/stoplist.properties" ),
@Parameter(name="ignoreCase", value="true")
})
})
public class Team {
...
}
Filters and char filters are applied in the order they are
defined in the @AnalyzerDef
annotation. Order
matters!
Some tokenizers, token filters or char filters load resources like
a configuration or metadata file. This is the case for the stop filter
and the synonym filter. If the resource charset is not using the VM
default, you can explicitly specify it by adding a
resource_charset
parameter.
Example 4.15. Use a specific charset to load the property file
@AnalyzerDef(name="customanalyzer",
charFilters = {
@CharFilterDef(factory = MappingCharFilterFactory.class, params = {
@Parameter(name = "mapping",
value = "org/hibernate/search/test/analyzer/solr/mapping-chars.properties")
})
},
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = ISOLatin1AccentFilterFactory.class),
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = StopFilterFactory.class, params = {
@Parameter(name="words",
value= "org/hibernate/search/test/analyzer/solr/stoplist.properties" ),
@Parameter(name="resource_charset", value = "UTF-16BE"),
@Parameter(name="ignoreCase", value="true")
})
})
public class Team {
...
}
Once defined, an analyzer definition can be reused by an
@Analyzer
declaration as seen in Example 4.16, “Referencing an
analyzer by name”.
Example 4.16. Referencing an analyzer by name
@Entity
@Indexed
@AnalyzerDef(name="customanalyzer", ... )
public class Team {
@Id
@DocumentId
@GeneratedValue
private Integer id;
@Field
private String name;
@Field
private String location;
@Field
@Analyzer(definition = "customanalyzer")
private String description;
}
Analyzer instances declared by @AnalyzerDef
are also available by their name in the
SearchFactory
which is quite useful wen building
queries.
Analyzer analyzer = fullTextSession.getSearchFactory().getAnalyzer("customanalyzer");
Fields in queries should be analyzed with the same analyzer used to index the field so that they speak a common "language": the same tokens are reused between the query and the indexing process. This rule has some exceptions but is true most of the time. Respect it unless you know what you are doing.
Solr and Lucene come with a lot of useful default char filters, tokenizers and filters. You can find a complete list of char filter factories, tokenizer factories and filter factories at http://wiki.apache.org/solr/AnalyzersTokenizersTokenFilters. Let's check a few of them.
Table 4.1. Example of available char filters
Factory | Description | Parameters | Additional dependencies |
---|---|---|---|
MappingCharFilterFactory | Replaces one or more characters with one or more characters, based on mappings specified in the resource file |
| none |
HTMLStripCharFilterFactory | Remove HTML standard tags, keeping the text | none | none |
Table 4.2. Example of available tokenizers
Factory | Description | Parameters | Additional dependencies |
---|---|---|---|
StandardTokenizerFactory | Use the Lucene StandardTokenizer | none | none |
HTMLStripCharFilterFactory | Remove HTML tags, keep the text and pass it to a StandardTokenizer. | none | solr-core |
PatternTokenizerFactory | Breaks text at the specified regular expression pattern. |
group: says which pattern group to extract into tokens | solr-core |
Table 4.3. Examples of available filters
Factory | Description | Parameters | Additional dependencies |
---|---|---|---|
StandardFilterFactory | Remove dots from acronyms and 's from words | none | solr-core |
LowerCaseFilterFactory | Lowercases all words | none | solr-core |
StopFilterFactory | Remove words (tokens) matching a list of stop words |
ignoreCase: true if
| solr-core |
SnowballPorterFilterFactory | Reduces a word to it's root in a given language. (eg. protect, protects, protection share the same root). Using such a filter allows searches matching related words. | language : Danish, Dutch, English,
Finnish, French, German, Italian, Norwegian, Portuguese,
Russian, Spanish, Swedish and a few more | solr-core |
ISOLatin1AccentFilterFactory | Remove accents for languages like French | none | solr-core |
PhoneticFilterFactory | Inserts phonetically similar tokens into the token stream |
inject:
| solr-core and
commons-codec |
CollationKeyFilterFactory | Converts each token into its
java.text.CollationKey , and then
encodes the CollationKey with
IndexableBinaryStringTools , to allow it
to be stored as an index term. | custom , language ,
country , variant ,
strength , decomposition
see Lucene's
CollationKeyFilter javadocs for more
info | solr-core and
commons-io |
We recommend to check all the implementations of
org.apache.solr.analysis.TokenizerFactory
and
org.apache.solr.analysis.TokenFilterFactory
in
your IDE to see the implementations available.
So far all the introduced ways to specify an analyzer were static.
However, there are use cases where it is useful to select an analyzer
depending on the current state of the entity to be indexed, for example
in a multilingual applications. For an BlogEntry
class for example the analyzer could depend on the language property of
the entry. Depending on this property the correct language specific
stemmer should be chosen to index the actual text.
To enable this dynamic analyzer selection Hibernate Search
introduces the AnalyzerDiscriminator
annotation.
Example 4.17, “Usage of @AnalyzerDiscriminator” demonstrates the usage
of this annotation.
Example 4.17. Usage of @AnalyzerDiscriminator
@Entity
@Indexed
@AnalyzerDefs({
@AnalyzerDef(name = "en",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = EnglishPorterFilterFactory.class
)
}),
@AnalyzerDef(name = "de",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = GermanStemFilterFactory.class)
})
})
public class BlogEntry {
@Id
@GeneratedValue
@DocumentId
private Integer id;
@Field
@AnalyzerDiscriminator(impl = LanguageDiscriminator.class)
private String language;
@Field
private String text;
private Set<BlogEntry> references;
// standard getter/setter
...
}
public class LanguageDiscriminator implements Discriminator {
public String getAnalyzerDefinitionName(Object value, Object entity, String field) {
if ( value == null || !( entity instanceof Article ) ) {
return null;
}
return (String) value;
}
}
The prerequisite for using
@AnalyzerDiscriminator
is that all analyzers
which are going to be used dynamically are predefined via
@AnalyzerDef
definitions. If this is the case,
one can place the @AnalyzerDiscriminator
annotation either on the class or on a specific property of the entity
for which to dynamically select an analyzer. Via the
impl
parameter of the
AnalyzerDiscriminator
you specify a concrete
implementation of the Discriminator
interface. It
is up to you to provide an implementation for this interface. The only
method you have to implement is
getAnalyzerDefinitionName()
which gets called for
each field added to the Lucene document. The entity which is getting
indexed is also passed to the interface method. The
value
parameter is only set if the
AnalyzerDiscriminator
is placed on property level
instead of class level. In this case the value represents the current
value of this property.
An implemention of the Discriminator
interface has to return the name of an existing analyzer definition or
null
if the default analyzer should not be
overridden. Example 4.17, “Usage of @AnalyzerDiscriminator” assumes
that the language parameter is either 'de' or 'en' which matches the
specified names in the @AnalyzerDef
s.
In some situations retrieving analyzers can be handy. For example, if your domain model makes use of multiple analyzers (maybe to benefit from stemming, use phonetic approximation and so on), you need to make sure to use the same analyzers when you build your query.
This rule can be broken but you need a good reason for it. If you are unsure, use the same analyzers. If you use the Hibernate Search query DSL (see Section 5.1.2, “Building a Lucene query with the Hibernate Search query DSL”), you don't have to think about it. The query DSL does use the right analyzer transparently for you.
Whether you are using the Lucene programmatic API or the Lucene query parser, you can retrieve the scoped analyzer for a given entity. A scoped analyzer is an analyzer which applies the right analyzers depending on the field indexed. Remember, multiple analyzers can be defined on a given entity each one working on an individual field. A scoped analyzer unifies all these analyzers into a context-aware analyzer. While the theory seems a bit complex, using the right analyzer in a query is very easy.
Example 4.18. Using the scoped analyzer when building a full-text query
org.apache.lucene.queryParser.QueryParser parser = new QueryParser(
"title",
fullTextSession.getSearchFactory().getAnalyzer( Song.class )
);
org.apache.lucene.search.Query luceneQuery =
parser.parse( "title:sky Or title_stemmed:diamond" );
org.hibernate.Query fullTextQuery =
fullTextSession.createFullTextQuery( luceneQuery, Song.class );
List result = fullTextQuery.list(); //return a list of managed objects
In the example above, the song title is indexed in two fields: the
standard analyzer is used in the field title
and a
stemming analyzer is used in the field title_stemmed
.
By using the analyzer provided by the search factory, the query uses the
appropriate analyzer depending on the field targeted.
You can also retrieve analyzers defined via
@AnalyzerDef
by their definition name using
searchFactory.getAnalyzer(String)
.
When discussing the basic mapping for an entity one important fact
was so far disregarded. In Lucene all index fields have to be represented
as strings. All entity properties annotated with @Field
have to be converted to strings to be indexed. The reason we have not
mentioned it so far is, that for most of your properties Hibernate Search
does the translation job for you thanks to a set of built-in bridges.
However, in some cases you need a more fine grained control over the
translation process.
Hibernate Search comes bundled with a set of built-in bridges between a Java property type and its full text representation.
Per default null
elements are not
indexed. Lucene does not support null elements. However, in some
situation it can be useful to insert a custom token representing
the null
value. See Section 4.1.1.2, “@Field” for more information.
Strings are indexed as are
Numbers are converted into their string representation. Note that numbers cannot be compared by Lucene (ie used in ranged queries) out of the box: they have to be padded
Using a Range query has drawbacks; an alternative approach is to use a Filter query which will filter the result query to the appropriate range.
Hibernate Search will support a padding mechanism
Dates are stored as yyyyMMddHHmmssSSS in GMT time (200611072203012 for Nov 7th of 2006 4:03PM and 12ms EST). You shouldn't really bother with the internal format. What is important is that when using a TermRangeQuery, you should know that the dates have to be expressed in GMT time.
Usually, storing the date up to the millisecond is not
necessary. @DateBridge
defines the appropriate
resolution you are willing to store in the index
(@DateBridge(resolution=Resolution.DAY)
). The
date pattern will then be truncated accordingly.
@Entity
@Indexed
public class Meeting {
@Field(analyze=Analyze.NO)
@DateBridge(resolution=Resolution.MINUTE)
private Date date;
...
A Date whose resolution is lower than
MILLISECOND
cannot be a
@DocumentId
The default Date
bridge uses
Lucene's DateTools
to convert from and to
String
. This means that all dates are
expressed in GMT time. If your requirements are to store dates
in a fixed time zone you have to implement a custom date bridge.
Make sure you understand the requirements of your applications
regarding to date indexing and searching.
URI and URL are converted to their string representation
Class are converted to their fully qualified class name. The thread context classloader is used when the class is rehydrated
Hibernate Search allows you to extract text from various document
types using the built-in TikaBridge
which
utilizes Apache Tika to
extract text and metadata from the provided documents. The
TikaBridge
annotation can be used with
String
, URI
,
byte[]
or java.sql.Blob
properties. In the case of String
and
URI
the bridge interprets the values are file
paths and tries to open a file to parse the document. In the case of
byte[]
and Blob
the values
are directly passed to Tika for parsing.
Tika uses metadata as in- and output of the parsing process and it
also allows to provide additional context information. This process is
described in Parser
interface. The Hibernate Search Tika bridge allows you to make
use of these additional configuration options by providing two
interfaces in conjunction with TikaBridge
. The
first interface is the TikaParseContextProvider
.
It allows you to create a custom ParseContext
for
the document parsing. The second interface is
TikaMetadataProcessor
which has two methods -
prepareMetadata()
and set(String,
Object, Document, LuceneOptions, Metadata metadata)
. The
former allows to add additional metadata to the parsing process (for
example the file name) and the latter allows you to index metadata
discovered during the parsing process.
TikaParseContextProvider
as well as
TikaMetadataProcessor
implementation classes can
both be specified as parameters on the TikaBridge annotation.
Example 4.19. Example mapping with Apache Tika
@Entity
@Indexed
public class Song {
@Id
@GeneratedValue
long id;
@Field
@TikaBridge(metadataProcessor = Mp3TikaMetadataProcessor.class)
String mp3FileName;
[...]
}
QueryBuilder queryBuilder = fullTextSession.getSearchFactory()
.buildQueryBuilder()
.forEntity( Song.class )
.get();
Query query = queryBuilder.keyword()
.onField( "mp3FileName" )
.ignoreFieldBridge() //mandatory
.matching( "Apes" )
.createQuery();
List result = fullTextSession.createFullTextQuery( query ).list();
In the Example 4.19, “Example mapping with Apache Tika” the property
mp3FileName
represents a path to an MP3 file;
the headers of this file will be indexed and so the performed query will
be able to match the MP3 metadata.
TikaBridge does not implement TwoWayFieldBridge: queries built
using the DSL (as in the Example 4.19, “Example mapping with Apache Tika”) need
to explicitly enable the option
ignoreFieldBridge()
.
Sometimes, the built-in bridges of Hibernate Search do not cover some of your property types, or the String representation used by the bridge does not meet your requirements. The following paragraphs describe several solutions to this problem.
The simplest custom solution is to give Hibernate Search an
implementation of your expected Object
to
String
bridge. To do so you need to implement
the org.hibernate.search.bridge.StringBridge
interface. All implementations have to be thread-safe as they are used
concurrently.
Example 4.20. Custom StringBridge
implementation
/**
* Padding Integer bridge.
* All numbers will be padded with 0 to match 5 digits
*
* @author Emmanuel Bernard
*/
public class PaddedIntegerBridge implements StringBridge {
private int padding = 5;
public String objectToString(Object object) {
String rawInteger = ((Integer) object).toString();
if (rawInteger.length() > padding)
throw new IllegalArgumentException("Number too big to be padded");
StringBuilder paddedInteger = new StringBuilder();
for (int padIndex = rawInteger.length(); padIndex < padding; padIndex++) {
paddedInteger.append('0');
}
return paddedInteger.append( rawInteger ).toString();
}
}
Given the string bridge defined in Example 4.20, “Custom StringBridge
implementation”, any property or field can
use this bridge thanks to the @FieldBridge
annotation:
@FieldBridge(impl = PaddedIntegerBridge.class)
private Integer length;
Parameters can also be passed to the bridge implementation
making it more flexible. Example 4.21, “Passing parameters to your bridge implementation” implements a
ParameterizedBridge
interface and parameters
are passed through the @FieldBridge
annotation.
Example 4.21. Passing parameters to your bridge implementation
public class PaddedIntegerBridge implements StringBridge, ParameterizedBridge {
public static String PADDING_PROPERTY = "padding";
private int padding = 5; //default
public void setParameterValues(Map<String,String> parameters) {
String padding = parameters.get( PADDING_PROPERTY );
if (padding != null) this.padding = Integer.parseInt( padding );
}
public String objectToString(Object object) {
String rawInteger = ((Integer) object).toString();
if (rawInteger.length() > padding)
throw new IllegalArgumentException("Number too big to be padded");
StringBuilder paddedInteger = new StringBuilder( );
for (int padIndex = rawInteger.length(); padIndex < padding; padIndex++) {
paddedInteger.append('0');
}
return paddedInteger.append(rawInteger).toString();
}
}
//on the property:
@FieldBridge(impl = PaddedIntegerBridge.class,
params = @Parameter(name="padding", value="10")
)
private Integer length;
The ParameterizedBridge
interface can
be implemented by StringBridge
,
TwoWayStringBridge
,
FieldBridge
implementations.
All implementations have to be thread-safe, but the parameters are set during initialization and no special care is required at this stage.
It is sometimes useful to get the type the bridge is applied on:
the return type of the property for field/getter-level bridges
the class type for class-level bridges
An example is a bridge that deals with enums in a custom
fashion but needs to access the actual enum type. Any bridge
implementing AppliedOnTypeAwareBridge
will
get the type the bridge is applied on injected. Like parameters, the
type injected needs no particular care with regard to
thread-safety.
If you expect to use your bridge implementation on an id
property (ie annotated with @DocumentId
), you
need to use a slightly extended version of
StringBridge
named
TwoWayStringBridge
. Hibernate Search needs to
read the string representation of the identifier and generate the
object out of it. There is no difference in the way the
@FieldBridge
annotation is used.
Example 4.22. Implementing a TwoWayStringBridge usable for id properties
public class PaddedIntegerBridge implements TwoWayStringBridge, ParameterizedBridge {
public static String PADDING_PROPERTY = "padding";
private int padding = 5; //default
public void setParameterValues(Map parameters) {
Object padding = parameters.get(PADDING_PROPERTY);
if (padding != null) this.padding = (Integer) padding;
}
public String objectToString(Object object) {
String rawInteger = ((Integer) object).toString();
if (rawInteger.length() > padding)
throw new IllegalArgumentException("Number too big to be padded");
StringBuilder paddedInteger = new StringBuilder();
for (int padIndex = rawInteger.length(); padIndex < padding ; padIndex++) {
paddedInteger.append('0');
}
return paddedInteger.append(rawInteger).toString();
}
public Object stringToObject(String stringValue) {
return new Integer(stringValue);
}
}
//On an id property:
@DocumentId
@FieldBridge(impl = PaddedIntegerBridge.class,
params = @Parameter(name="padding", value="10")
private Integer id;
It is important for the two-way process to be idempotent (ie object = stringToObject( objectToString( object ) ) ).
Some use cases require more than a simple object to string
translation when mapping a property to a Lucene index. To give you the
greatest possible flexibility you can also implement a bridge as a
FieldBridge
. This interface gives you a
property value and let you map it the way you want in your Lucene
Document
. You can for example store a property
in two different document fields. The interface is very similar in its
concept to the Hibernate UserType
s.
Example 4.23. Implementing the FieldBridge interface
/**
* Store the date in 3 different fields - year, month, day - to ease Range Query per
* year, month or day (eg get all the elements of December for the last 5 years).
* @author Emmanuel Bernard
*/
public class DateSplitBridge implements FieldBridge {
private final static TimeZone GMT = TimeZone.getTimeZone("GMT");
public void set(String name, Object value, Document document, LuceneOptions luceneOptions) {
Date date = (Date) value;
Calendar cal = GregorianCalendar.getInstance(GMT);
cal.setTime(date);
int year = cal.get(Calendar.YEAR);
int month = cal.get(Calendar.MONTH) + 1;
int day = cal.get(Calendar.DAY_OF_MONTH);
// set year
luceneOptions.addFieldToDocument(
name + ".year",
String.valueOf( year ),
document );
// set month and pad it if needed
luceneOptions.addFieldToDocument(
name + ".month",
month < 10 ? "0" : "" + String.valueOf( month ),
document );
// set day and pad it if needed
luceneOptions.addFieldToDocument(
name + ".day",
day < 10 ? "0" : "" + String.valueOf( day ),
document );
}
}
//property @FieldBridge(impl = DateSplitBridge.class)
private Date date;
In Example 4.23, “Implementing the FieldBridge interface” the fields are not
added directly to Document. Instead the addition is delegated to the
LuceneOptions
helper; this helper will apply
the options you have selected on @Field
, like
Store
or TermVector
, or apply
the choosen @Boost
value. It is especially
useful to encapsulate the complexity of COMPRESS
implementations. Even though it is recommended to delegate to
LuceneOptions
to add fields to the
Document
, nothing stops you from editing the
Document
directly and ignore the
LuceneOptions
in case you need to.
Classes like LuceneOptions
are created
to shield your application from changes in Lucene API and simplify
your code. Use them if you can, but if you need more flexibility
you're not required to.
It is sometimes useful to combine more than one property of a
given entity and index this combination in a specific way into the
Lucene index. The @ClassBridge
respectively
@ClassBridges
annotations can be defined at
class level (as opposed to the property level). In this case the
custom field bridge implementation receives the entity instance as the
value parameter instead of a particular property. Though not shown in
Example 4.24, “Implementing a class bridge”,
@ClassBridge
supports the
termVector
attribute discussed in section
Section 4.1.1, “Basic mapping”.
Example 4.24. Implementing a class bridge
@Entity
@Indexed @ClassBridge(name="branchnetwork",
store=Store.YES,
impl = CatFieldsClassBridge.class,
params = @Parameter( name="sepChar", value=" " ) )
public class Department {
private int id;
private String network;
private String branchHead;
private String branch;
private Integer maxEmployees
...
}
public class CatFieldsClassBridge implements FieldBridge, ParameterizedBridge {
private String sepChar;
public void setParameterValues(Map parameters) {
this.sepChar = (String) parameters.get( "sepChar" );
}
public void set( String name, Object value, Document document, LuceneOptions luceneOptions) {
// In this particular class the name of the new field was passed
// from the name field of the ClassBridge Annotation. This is not
// a requirement. It just works that way in this instance. The
// actual name could be supplied by hard coding it below.
Department dep = (Department) value;
String fieldValue1 = dep.getBranch();
if ( fieldValue1 == null ) {
fieldValue1 = "";
}
String fieldValue2 = dep.getNetwork();
if ( fieldValue2 == null ) {
fieldValue2 = "";
}
String fieldValue = fieldValue1 + sepChar + fieldValue2;
Field field = new Field( name, fieldValue, luceneOptions.getStore(),
luceneOptions.getIndex(), luceneOptions.getTermVector() );
field.setBoost( luceneOptions.getBoost() );
document.add( field );
}
}
In this example, the particular
CatFieldsClassBridge
is applied to the
department
instance, the field bridge then
concatenate both branch and network and index the
concatenation.
This feature is considered experimental. More operation types might be added in the future depending on user feedback.
In some situations, you want to index an entity only when it is in a given state, for example:
only index blog entries marked as published
no longer index invoices when they are marked archived
This serves both functional and technical needs. You don't want your blog readers to find your draft entries and filtering them off the query is a bit annoying. Very few of your entities are actually required to be indexed and you want to limit indexing overhead and keep indexes small and fast.
Hibernate Search lets you intercept entity indexing operations and override them. It is quite simple:
Write an EntityIndexingInterceptor
class
with your entity state based logic
Mark the entity as intercepted by this implementation
Let's look at the blog example at Example 4.25, “Index blog entries only when they are published and remove them when they are in a different state”
Example 4.25. Index blog entries only when they are published and remove them when they are in a different state
/**
* Only index blog when it is in published state
*
* @author Emmanuel Bernard <emmanuel@hibernate.org>
*/
public class IndexWhenPublishedInterceptor implements EntityIndexingInterceptor<Blog> {
@Override
public IndexingOverride onAdd(Blog entity) {
if (entity.getStatus() == BlogStatus.PUBLISHED) {
return IndexingOverride.APPLY_DEFAULT;
}
return IndexingOverride.SKIP;
}
@Override
public IndexingOverride onUpdate(Blog entity) {
if (entity.getStatus() == BlogStatus.PUBLISHED) {
return IndexingOverride.UPDATE;
}
return IndexingOverride.REMOVE;
}
@Override
public IndexingOverride onDelete(Blog entity) {
return IndexingOverride.APPLY_DEFAULT;
}
@Override
public IndexingOverride onCollectionUpdate(Blog entity) {
return onUpdate(entity);
}
}
@Entity
@Indexed(interceptor=IndexWhenPublishedInterceptor.class)
public class Blog {
@Id
@GeneratedValue
public Integer getId() { return id; }
public void setId(Integer id) { this.id = id; }
private Integer id;
@Field
public String getTitle() { return title; }
public void setTitle(String title) { this.title = title; }
private String title;
public BlogStatus getStatus() { return status; }
public void setStatus(BlogStatus status) { this.status = status; }
private BlogStatus status;
[...]
}
We mark the Blog
entity with
@Indexed.interceptor
. As you can see,
IndexWhenPublishedInterceptor
implements
EntityIndexingInterceptor
and accepts
Blog
entities (it could have accepted superclasses
as well - for example Object
if you create a
generic interceptor.
You can react to several planned indexing events:
when an entity is added to your datastore
when an entity is updated in your datastore
when an entity is deleted from your datastore
when a collection own by this entity is updated in your datastore
For each occurring event you can respond with one of the following actions:
APPLY_DEFAULT
: that's the basic operation
that lets Hibernate Search update the index as expected - creating,
updating or removing the document
SKIP
: ask Hibernate Search to not do anything
to the index for this event - data will not be created, updated or
removed from the index in any way
REMOVE
: ask Hibernate Search to remove
indexing data about this entity - you can safely ask for
REMOVE
even if the entity has not yet been
indexed
UPDATE
: ask Hibernate Search to either index
or update the index for this entity - it is safe to ask for
UPDATE
even if the entity has never been
indexed
Be careful, not every combination makes sense: for example, asking
to UPDATE
the index upon
onDelete
. Note that you could ask for
SKIP
in this situation if saving indexing time is
critical for you. That's rarely the case though.
By default, no interceptor is applied on an entity. You have to
explicitly define an interceptor via the @Indexed
annotation (see Section 4.1.1.1, “@Indexed”) or programmatically
(see Section 4.7, “Programmatic API”). This class and
all its subclasses will then be intercepted. You can stop or change the
interceptor used in a subclass by overriding
@Indexed.interceptor
. Hibernate Search provides
DontInterceptEntityInterceptor
which will
explicitly not intercept any call. This is useful to reset interception
within a class hierarchy.
Dirty checking optimization is disabled when interceptors are used. Dirty checking optimization does check what has changed in an entity and only triggers an index update if indexed properties are changed. The reason is simple, your interceptor might depend on a non indexed property which would be ignored by this optimization.
An EntityIndexingInterceptor
can never
override an explicit indexing operation such as
index(T)
, purge(T, id)
or purgeAll(class)
.
You can provide your own id for Hibernate Search if you are extending the internals. You will have to generate a unique value so it can be given to Lucene to be indexed. This will have to be given to Hibernate Search when you create an org.hibernate.search.Work object - the document id is required in the constructor.
Unlike @DocumentId
which is applied on field
level, @ProvidedId
is used on the class level.
Optionally you can specify your own bridge implementation using the
bridge
property. Also, if you annotate a class with
@ProvidedId
, your subclasses will also get the
annotation - but it is not done by using the
java.lang.annotations.@Inherited. Be sure however, to
not use this annotation with @DocumentId as your
system will break.
Example 4.26. Providing your own id
@ProvidedId(bridge = org.my.own.package.MyCustomBridge)
@Indexed
public class MyClass{
@Field
String MyString;
...
}
Although the recommended approach for mapping indexed entities is to use annotations, it is sometimes more convenient to use a different approach:
the same entity is mapped differently depending on deployment needs (customization for clients)
some automatization process requires the dynamic mapping of many entities sharing common traits
While it has been a popular demand in the past, the Hibernate team never found the idea of an XML alternative to annotations appealing due to it's heavy duplication, lack of code refactoring safety, because it did not cover all the use case spectrum and because we are in the 21st century :)
The idea of a programmatic API was much more appealing and has now become a reality. You can programmatically define your mapping using a programmatic API: you define entities and fields as indexable by using mapping classes which effectively mirror the annotation concepts in Hibernate Search. Note that fan(s) of XML approach can design their own schema and use the programmatic API to create the mapping while parsing the XML stream.
In order to use the programmatic model you must first construct a
SearchMapping
object which you can do in two
ways:
directly
via a factory
You can pass the SearchMapping
object
directly via the property key
hibernate.search.model_mapping
or the constant
Environment.MODEL_MAPPING
. Use the
Configuration
API or the Map passed to the JPA
Persistence
bootstrap methods.
Example 4.27. Programmatic mapping
SearchMapping mapping = new SearchMapping();
[...] //configure mapping
Configuration config = new Configuration();
config.getProperties().put( Environment.MODEL_MAPPING, mapping );
SessionFactory sf = config.buildSessionFactory();
Example 4.28. Programmatic mapping with JPA
SearchMapping mapping = new SearchMapping();
[...] //configure mapping
Map props = new HashMap();
props.put( Environment.MODEL_MAPPING, mapping );
EntityManagerFactory emf = Persistence.createEntityManagerFactory( "userPU", props );
Alternatively, you can create a factory class (ie. hosting a method
annotated with @Factory
) whose factory method
returns the SearchMapping
object. The factory class
must have a no-arg constructor and its fully qualified class name is
passed to the property key
hibernate.search.model_mapping
or its type-safe
representation Environment.MODEL_MAPPING
. This
approach is useful when you do not necessarily control the bootstrap
process like in a Java EE, CDI or Spring Framework container.
Example 4.29. Use a mapping factory
public class MyAppSearchMappingFactory {
@Factory
public SearchMapping getSearchMapping() {
SearchMapping mapping = new SearchMapping();
mapping
.analyzerDef( "ngram", StandardTokenizerFactory.class )
.filter( LowerCaseFilterFactory.class )
.filter( NGramFilterFactory.class )
.param( "minGramSize", "3" )
.param( "maxGramSize", "3" );
return mapping;
}
}
<persistence ...>
<persistence-unit name="users">
...
<properties>
<property name="hibernate.search.model_mapping"
value="com.acme.MyAppSearchMappingFactory"/>
</properties>
</persistence-unit>
</persistence>
The SearchMapping
is the root object which
contains all the necessary indexable entities and fields. From there, the
SearchMapping
object exposes a fluent (and thus
intuitive) API to express your mappings: it contextually exposes the
relevant mapping options in a type-safe way. Just let your IDE
autocompletion feature guide you through.
Today, the programmatic API cannot be used on a class annotated with
Hibernate Search annotations, chose one approach or the other. Also note
that the same default values apply in annotations and the programmatic
API. For example, the @Field.name
is defaulted to
the property name and does not have to be set.
Each core concept of the programmatic API has a corresponding example to depict how the same definition would look using annotation. Therefore seeing an annotation example of the programmatic approach should give you a clear picture of what Hibernate Search will build with the marked entities and associated properties.
The first concept of the programmatic API is to define an entity
as indexable. Using the annotation approach a user would mark the entity
as @Indexed
, the following example demonstrates
how to programmatically achieve this.
Example 4.30. Marking an entity indexable
SearchMapping mapping = new SearchMapping();
mapping.entity(Address.class)
.indexed()
.indexName("Address_Index") //optional
.interceptor(IndexWhenPublishedInterceptor.class); //optional
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
As you can see you must first create a
SearchMapping
object which is the root object
that is then passed to the Configuration
object
as property. You must declare an entity and if you wish to make that
entity as indexable then you must call the
indexed()
method. The indexed()
method has an optional indexName(String
indexName)
which can be used to change the default index
name that is created by Hibernate Search. Likewise, an
interceptor(Class<? extends
EntityIndexedInterceptor>)
is available. Using the
annotation model the above can be achieved as:
Example 4.31. Annotation example of indexing entity
@Entity
@Indexed(index="Address_Index", interceptor=IndexWhenPublishedInterceptor.class)
public class Address {
....
}
To set a property as a document id:
Example 4.32. Enabling document id with programmatic model
SearchMapping mapping = new SearchMapping();
mapping.entity(Address.class).indexed()
.property("addressId", ElementType.FIELD) //field access
.documentId()
.name("id");
cfg.getProperties().put( "hibernate.search.model_mapping", mapping);
The above is equivalent to annotating a property in the entity as
@DocumentId
as seen in the following
example:
Example 4.33. DocumentId annotation definition
@Entity
@Indexed
public class Address {
@Id
@GeneratedValue
@DocumentId(name="id")
private Long addressId;
....
}
The next section demonstrates how to programmatically define analyzers.
Analyzers can be programmatically defined using the
analyzerDef(String analyzerDef, Class<? extends
TokenizerFactory> tokenizerFactory)
method. This method
also enables you to define filters for the analyzer definition. Each
filter that you define can optionally take in parameters as seen in the
following example :
Example 4.34. Defining analyzers using programmatic model
SearchMapping mapping = new SearchMapping();
mapping
.analyzerDef( "ngram", StandardTokenizerFactory.class ) .filter( LowerCaseFilterFactory.class ) .filter( NGramFilterFactory.class ) .param( "minGramSize", "3" ) .param( "maxGramSize", "3" ) .analyzerDef( "en", StandardTokenizerFactory.class ) .filter( LowerCaseFilterFactory.class ) .filter( EnglishPorterFilterFactory.class ) .analyzerDef( "de", StandardTokenizerFactory.class ) .filter( LowerCaseFilterFactory.class ) .filter( GermanStemFilterFactory.class )
.entity(Address.class).indexed()
.property("addressId", ElementType.METHOD) //getter access
.documentId()
.name("id");
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The analyzer mapping defined above is equivalent to the annotation
model using @AnalyzerDef
in conjunction with
@AnalyzerDefs
:
Example 4.35. Analyzer definition using annotation
@Indexed
@Entity
@AnalyzerDefs({
@AnalyzerDef(name = "ngram",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = NGramFilterFactory.class,
params = {
@Parameter(name = "minGramSize",value = "3"),
@Parameter(name = "maxGramSize",value = "3")
})
}),
@AnalyzerDef(name = "en",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = EnglishPorterFilterFactory.class)
}),
@AnalyzerDef(name = "de",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = GermanStemFilterFactory.class)
})
})
public class Address {
...
}
The programmatic API provides easy mechanism for defining full
text filter definitions which is available via
@FullTextFilterDef
and
@FullTextFilterDefs
(see Section 5.3, “Filters”). The next example depicts the creation of full
text filter definition using the fullTextFilterDef
method.
Example 4.36. Defining full text definition programmatically
SearchMapping mapping = new SearchMapping();
mapping
.analyzerDef( "en", StandardTokenizerFactory.class )
.filter( LowerCaseFilterFactory.class )
.filter( EnglishPorterFilterFactory.class )
.fullTextFilterDef("security", SecurityFilterFactory.class) .cache(FilterCacheModeType.INSTANCE_ONLY)
.entity(Address.class)
.indexed()
.property("addressId", ElementType.METHOD)
.documentId()
.name("id")
.property("street1", ElementType.METHOD)
.field()
.analyzer("en")
.store(Store.YES)
.field()
.name("address_data")
.analyzer("en")
.store(Store.NO);
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The previous example can effectively been seen as annotating your
entity with @FullTextFilterDef
like below:
Example 4.37. Using annotation to define full text filter definition
@Entity
@Indexed
@AnalyzerDefs({
@AnalyzerDef(name = "en",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = EnglishPorterFilterFactory.class)
})
})
@FullTextFilterDefs({
@FullTextFilterDef(name = "security", impl = SecurityFilterFactory.class, cache = FilterCacheModeType.INSTANCE_ONLY)
})
public class Address {
@Id
@GeneratedValue
@DocumentId(name="id")
pubblic Long getAddressId() {...};
@Fields({
@Field(store=Store.YES, analyzer=@Analyzer(definition="en")),
@Field(name="address_data", analyzer=@Analyzer(definition="en"))
})
public String getAddress1() {...};
......
}
When defining fields for indexing using the programmatic API, call
field()
on the property(String
propertyName, ElementType elementType)
method. From
field()
you can specify the name,
index
, store
,
bridge
and analyzer
definitions.
Example 4.38. Indexing fields using programmatic API
SearchMapping mapping = new SearchMapping();
mapping
.analyzerDef( "en", StandardTokenizerFactory.class )
.filter( LowerCaseFilterFactory.class )
.filter( EnglishPorterFilterFactory.class )
.entity(Address.class).indexed()
.property("addressId", ElementType.METHOD)
.documentId()
.name("id")
.property("street1", ElementType.METHOD)
.field() .analyzer("en") .store(Store.YES) .field() .name("address_data") .analyzer("en");
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The above example of marking fields as indexable is equivalent to
defining fields using @Field
as seen
below:
Example 4.39. Indexing fields using annotation
@Entity
@Indexed
@AnalyzerDefs({
@AnalyzerDef(name = "en",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
filters = {
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = EnglishPorterFilterFactory.class)
})
})
public class Address {
@Id
@GeneratedValue
@DocumentId(name="id")
private Long getAddressId() {...};
@Fields({
@Field(store=Store.YES, analyzer=@Analyzer(definition="en")),
@Field(name="address_data", analyzer=@Analyzer(definition="en"))
})
public String getAddress1() {...}
......
}
When using a programmatic mapping for a given type X, you can only refer to fields defined on X. Fields or methods inherited from a super type are not configurable. In case you need to configure a super class property, you need to either override the property in X or create a programmatic mapping for the super class. This mimics the usage of annotations where you cannot annotate a field or method of a super class either, unless it is redefined in the given type.
In this section you will see how to programmatically define
entities to be embedded into the indexed entity similar to using the
@IndexedEmbedded
model. In order to define this
you must mark the property as
indexEmbedded.
There is the option to add a
prefix to the embedded entity definition which can be done by calling
prefix
as seen in the example below:
Example 4.40. Programmatically defining embedded entites
SearchMapping mapping = new SearchMapping();
mapping
.entity(ProductCatalog.class)
.indexed()
.property("catalogId", ElementType.METHOD)
.documentId()
.name("id")
.property("title", ElementType.METHOD)
.field()
.index(Index.YES)
.store(Store.NO)
.property("description", ElementType.METHOD)
.field()
.index(Index.YES)
.store(Store.NO)
.property("items", ElementType.METHOD)
.indexEmbedded() .prefix("catalog.items"); //optional
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The next example shows the same definition using annotation
(@IndexedEmbedded
):
Example 4.41. Using @IndexedEmbedded
@Entity
@Indexed
public class ProductCatalog {
@Id
@GeneratedValue
@DocumentId(name="id")
public Long getCatalogId() {...}
@Field
public String getTitle() {...}
@Field
public String getDescription();
@OneToMany(fetch = FetchType.LAZY)
@IndexColumn(name = "list_position")
@Cascade(org.hibernate.annotations.CascadeType.ALL)
@IndexedEmbedded(prefix="catalog.items")
public List<Item> getItems() {...}
...
}
@ContainedIn
can be define as seen in the
example below:
Example 4.42. Programmatically defining ContainedIn
SearchMapping mapping = new SearchMapping();
mapping
.entity(ProductCatalog.class)
.indexed()
.property("catalogId", ElementType.METHOD)
.documentId()
.property("title", ElementType.METHOD)
.field()
.property("description", ElementType.METHOD)
.field()
.property("items", ElementType.METHOD)
.indexEmbedded()
.entity(Item.class)
.property("description", ElementType.METHOD)
.field()
.property("productCatalog", ElementType.METHOD)
.containedIn();
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
This is equivalent to defining @ContainedIn
in your entity:
Example 4.43. Annotation approach for ContainedIn
@Entity
@Indexed
public class ProductCatalog {
@Id
@GeneratedValue
@DocumentId
public Long getCatalogId() {...}
@Field
public String getTitle() {...}
@Field
public String getDescription() {...}
@OneToMany(fetch = FetchType.LAZY)
@IndexColumn(name = "list_position")
@Cascade(org.hibernate.annotations.CascadeType.ALL)
@IndexedEmbedded
private List<Item> getItems() {...}
...
}
@Entity
public class Item {
@Id
@GeneratedValue
private Long itemId;
@Field
public String getDescription() {...}
@ManyToOne( cascade = { CascadeType.PERSIST, CascadeType.REMOVE } )
@ContainedIn
public ProductCatalog getProductCatalog() {...}
...
}
In order to define a calendar or date bridge mapping, call the
dateBridge(Resolution resolution)
or
calendarBridge(Resolution resolution)
methods
after you have defined a field()
in the
SearchMapping
hierarchy.
Example 4.44. Programmatic model for defining calendar/date bridge
SearchMapping mapping = new SearchMapping();
mapping
.entity(Address.class)
.indexed()
.property("addressId", ElementType.FIELD)
.documentId()
.property("street1", ElementType.FIELD()
.field()
.property("createdOn", ElementType.FIELD)
.field()
.dateBridge(Resolution.DAY)
.property("lastUpdated", ElementType.FIELD)
.calendarBridge(Resolution.DAY);
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
See below for defining the above using
@CalendarBridge
and
@DateBridge
:
Example 4.45. @CalendarBridge and @DateBridge definition
@Entity
@Indexed
public class Address {
@Id
@GeneratedValue
@DocumentId
private Long addressId;
@Field
private String address1;
@Field
@DateBridge(resolution=Resolution.DAY)
private Date createdOn;
@CalendarBridge(resolution=Resolution.DAY)
private Calendar lastUpdated;
...
}
It is possible to associate bridges to programmatically defined
fields. When you define a field()
programmatically you can use the bridge(Class<?>
impl)
to associate a FieldBridge
implementation class. The bridge method also provides
optional methods to include any parameters required for the bridge
class. The below shows an example of programmatically defining a
bridge:
Example 4.46. Defining field bridges programmatically
SearchMapping mapping = new SearchMapping();
mapping
.entity(Address.class)
.indexed()
.property("addressId", ElementType.FIELD)
.documentId()
.property("street1", ElementType.FIELD)
.field()
.field()
.name("street1_abridged")
.bridge( ConcatStringBridge.class ) .param( "size", "4" );
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The above can equally be defined using annotations, as seen in the next example.
Example 4.47. Defining field bridges using annotation
@Entity
@Indexed
public class Address {
@Id
@GeneratedValue
@DocumentId(name="id")
private Long addressId;
@Fields({
@Field,
@Field(name="street1_abridged",
bridge = @FieldBridge( impl = ConcatStringBridge.class,
params = @Parameter( name="size", value="4" ))
})
private String address1;
...
}
You can define class bridges on entities programmatically. This is shown in the next example:
Example 4.48. Defining class briges using API
SearchMapping mapping = new SearchMapping();
mapping
.entity(Departments.class) .classBridge(CatDeptsFieldsClassBridge.class) .name("branchnetwork") .index(Index.YES) .store(Store.YES) .param("sepChar", " ") .classBridge(EquipmentType.class) .name("equiptype") .index(Index.YES) .store(Store.YES) .param("C", "Cisco") .param("D", "D-Link") .param("K", "Kingston") .param("3", "3Com")
.indexed();
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The above is similar to using @ClassBridge
as seen in the next example:
Example 4.49. Using @ClassBridge
@Entity
@Indexed
@ClassBridges ( {
@ClassBridge(name="branchnetwork",
store= Store.YES,
impl = CatDeptsFieldsClassBridge.class,
params = @Parameter( name="sepChar", value=" " ) ),
@ClassBridge(name="equiptype",
store= Store.YES,
impl = EquipmentType.class,
params = {@Parameter( name="C", value="Cisco" ),
@Parameter( name="D", value="D-Link" ),
@Parameter( name="K", value="Kingston" ),
@Parameter( name="3", value="3Com" )
})
})
public class Departments {
....
}
You can apply a dynamic boost factor on either a field or a whole entity:
Example 4.50. DynamicBoost mapping using programmatic model
SearchMapping mapping = new SearchMapping();
mapping
.entity(DynamicBoostedDescLibrary.class)
.indexed()
.dynamicBoost(CustomBoostStrategy.class)
.property("libraryId", ElementType.FIELD)
.documentId().name("id")
.property("name", ElementType.FIELD)
.dynamicBoost(CustomFieldBoostStrategy.class);
.field()
.store(Store.YES)
cfg.getProperties().put( "hibernate.search.model_mapping", mapping );
The next example shows the equivalent mapping using the
@DynamicBoost
annotation:
Example 4.51. Using the @DynamicBoost
@Entity
@Indexed
@DynamicBoost(impl = CustomBoostStrategy.class)
public class DynamicBoostedDescriptionLibrary {
@Id
@GeneratedValue
@DocumentId
private int id;
private float dynScore;
@Field(store = Store.YES)
@DynamicBoost(impl = CustomFieldBoostStrategy.class)
private String name;
public DynamicBoostedDescriptionLibrary() {
dynScore = 1.0f;
}
.......
}
The second most important capability of Hibernate Search is the ability to execute Lucene queries and retrieve entities managed by a Hibernate session. The search provides the power of Lucene without leaving the Hibernate paradigm, giving another dimension to the Hibernate classic search mechanisms (HQL, Criteria query, native SQL query).
Preparing and executing a query consists of four simple steps:
Creating a FullTextSession
Creating a Lucene query either via the Hibernate Search query DSL (recommended) or by utilizing the Lucene query API
Wrapping the Lucene query using an
org.hibernate.Query
Executing the search by calling for example
list()
or
scroll()
To access the querying facilities, you have to use a
FullTextSession
. This Search specific session wraps a
regular org.hibernate.Session
in order to provide
query and indexing capabilities.
Example 5.1. Creating a FullTextSession
Session session = sessionFactory.openSession();
...
FullTextSession fullTextSession = Search.getFullTextSession(session);
Once you have a FullTextSession
you have two
options to build the full-text query: the Hibernate Search query DSL or the
native Lucene query.
If you use the Hibernate Search query DSL, it will look like this:
QueryBuilder b = fullTextSession.getSearchFactory()
.buildQueryBuilder().forEntity(Myth.class).get();
org.apache.lucene.search.Query luceneQuery =
b.keyword()
.onField("history").boostedTo(3)
.matching("storm")
.createQuery();
org.hibernate.Query fullTextQuery = fullTextSession.createFullTextQuery(luceneQuery);
List result = fullTextQuery.list(); //return a list of managed objects
You can alternatively write your Lucene query either using the Lucene query parser or Lucene programmatic API.
Example 5.2. Creating a Lucene query via the
QueryParser
SearchFactory searchFactory = fullTextSession.getSearchFactory();
org.apache.lucene.queryParser.QueryParser parser =
new QueryParser("title", searchFactory.getAnalyzer(Myth.class));
try {
org.apache.lucene.search.Query luceneQuery = parser.parse("history:storm^3");
}
catch (ParseException e) {
//handle parsing failure
}
org.hibernate.Query fullTextQuery = fullTextSession.createFullTextQuery(luceneQuery);
List result = fullTextQuery.list(); //return a list of managed objects
The Hibernate query built on top of the Lucene query is a regular
org.hibernate.Query
, which means you are in the same
paradigm as the other Hibernate query facilities (HQL, Native or
Criteria). The regular list()
,
uniqueResult()
, iterate()
and
scroll()
methods can be used.
In case you are using the Java Persistence APIs of Hibernate, the same extensions exist:
Example 5.3. Creating a Search query using the JPA API
EntityManager em = entityManagerFactory.createEntityManager();
FullTextEntityManager fullTextEntityManager =
org.hibernate.search.jpa.Search.getFullTextEntityManager(em);
...
QueryBuilder b = fullTextEntityManager.getSearchFactory()
.buildQueryBuilder().forEntity( Myth.class ).get();
org.apache.lucene.search.Query luceneQuery =
b.keyword()
.onField("history").boostedTo(3)
.matching("storm")
.createQuery(); javax.persistence.Query fullTextQuery = fullTextEntityManager.createFullTextQuery( luceneQuery );
List result = fullTextQuery.getResultList(); //return a list of managed objects
The following examples we will use the Hibernate APIs but the same
example can be easily rewritten with the Java Persistence API by just
adjusting the way the FullTextQuery
is
retrieved.
Hibernate Search queries are built on top of Lucene queries which
gives you total freedom on the type of Lucene query you want to execute.
However, once built, Hibernate Search wraps further query processing using
org.hibernate.Query
as your primary query
manipulation API.
Using the Lucene API, you have several options. You can use the query parser (fine for simple queries) or the Lucene programmatic API (for more complex use cases). It is out of the scope of this documentation on how to exactly build a Lucene query. Please refer to the online Lucene documentation or get hold of a copy of Lucene In Action or Hibernate Search in Action.
Writing full-text queries with the Lucene programmatic API is quite complex. It's even more complex to understand the code once written. Besides the inherent API complexity, you have to remember to convert your parameters to their string equivalent as well as make sure to apply the correct analyzer to the right field (a ngram analyzer will for example use several ngrams as the tokens for a given word and should be searched as such).
The Hibernate Search query DSL makes use of a style of API called a fluent API. This API has a few key characteristics:
it has meaningful method names making a succession of operations reads almost like English
it limits the options offered to what makes sense in a given context (thanks to strong typing and IDE autocompletion).
It often uses the chaining method pattern
it's easy to use and even easier to read
Let's see how to use the API. You first need to create a query
builder that is attached to a given indexed entity type. This
QueryBuilder
will know what analyzer to use and
what field bridge to apply. You can create several
QueryBuilder
s (one for each entity type involved
in the root of your query). You get the
QueryBuilder
from the
SearchFactory
.
QueryBuilder mythQB = searchFactory.buildQueryBuilder().forEntity( Myth.class ).get();
You can also override the analyzer used for a given field or fields. This is rarely needed and should be avoided unless you know what you are doing.
QueryBuilder mythQB = searchFactory.buildQueryBuilder()
.forEntity( Myth.class )
.overridesForField("history","stem_analyzer_definition")
.get();
Using the query builder, you can then build queries. It is
important to realize that the end result of a
QueryBuilder
is a Lucene query. For this reason
you can easily mix and match queries generated via Lucene's query parser
or Query
objects you have assembled with the
Lucene programmatic API and use them with the Hibernate Search DSL. Just
in case the DSL is missing some features.
Let's start with the most basic use case - searching for a specific word:
Query luceneQuery = mythQB.keyword().onField("history").matching("storm").createQuery();
keyword()
means that you are trying to
find a specific word. onField()
specifies in
which Lucene field to look. matching()
tells
what to look for. And finally createQuery()
creates the Lucene query object. A lot is going on with this line of
code.
The value storm is passed through the
history
FieldBridge
: it
does not matter here but you will see that it's quite handy when
dealing with numbers or dates.
The field bridge value is then passed to the analyzer used
to index the field history
. This ensures that
the query uses the same term transformation than the indexing
(lower case, n-gram, stemming and so on). If the analyzing process
generates several terms for a given word, a boolean query is used
with the SHOULD
logic (roughly an
OR
logic).
Let's see how you can search a property that is not of type string.
@Entity
@Indexed
public class Myth {
@Field(analyze = Analyze.NO)
@DateBridge(resolution = Resolution.YEAR)
public Date getCreationDate() { return creationDate; }
public Date setCreationDate(Date creationDate) { this.creationDate = creationDate; }
private Date creationDate;
...
}
Date birthdate = ...;
Query luceneQuery = mythQb.keyword().onField("creationDate").matching(birthdate).createQuery();
In plain Lucene, you would have had to convert the
Date
object to its string representation (in
this case the year).
This conversion works for any object, not just
Date
, provided that the
FieldBridge
has an
objectToString
method (and all built-in
FieldBridge
implementations do).
We make the example a little more advanced now and have a look at how to search a field that uses ngram analyzers. ngram analyzers index succession of ngrams of your words which helps to recover from user typos. For example the 3-grams of the word hibernate are hib, ibe, ber, rna, nat, ate.
@AnalyzerDef(name = "ngram",
tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class ),
filters = {
@TokenFilterDef(factory = StandardFilterFactory.class),
@TokenFilterDef(factory = LowerCaseFilterFactory.class),
@TokenFilterDef(factory = StopFilterFactory.class),
@TokenFilterDef(factory = NGramFilterFactory.class,
params = {
@Parameter(name = "minGramSize", value = "3"),
@Parameter(name = "maxGramSize", value = "3") } )
}
)
@Entity
@Indexed
public class Myth {
@Field(analyzer=@Analyzer(definition="ngram")
@DateBridge(resolution = Resolution.YEAR)
public String getName() { return name; }
public String setName(Date name) { this.name = name; }
private String name;
...
}
Date birthdate = ...;
Query luceneQuery = mythQb.keyword().onField("name").matching("Sisiphus")
.createQuery();
The matching word "Sisiphus" will be lower-cased and then split
into 3-grams: sis, isi, sip, phu, hus. Each of these n-gram will be
part of the query. We will then be able to find the Sysiphus myth
(with a y
). All that is transparently done for
you.
If for some reason you do not want a specific field to use the
field bridge or the analyzer you can call the
ignoreAnalyzer()
or
ignoreFieldBridge()
functions
To search for multiple possible words in the same field, simply add them all in the matching clause.
//search document with storm or lightning in their history
Query luceneQuery =
mythQB.keyword().onField("history").matching("storm lightning").createQuery();
To search the same word on multiple fields, use the
onFields
method.
Query luceneQuery = mythQB
.keyword()
.onFields("history","description","name")
.matching("storm")
.createQuery();
Sometimes, one field should be treated differently from another
field even if searching the same term, you can use the
andField()
method for that.
Query luceneQuery = mythQB.keyword()
.onField("history")
.andField("name")
.boostedTo(5)
.andField("description")
.matching("storm")
.createQuery();
In the previous example, only field name is boosted to 5.
To execute a fuzzy query (based on the Levenshtein distance
algorithm), start like a keyword
query and add the
fuzzy flag.
Query luceneQuery = mythQB
.keyword()
.fuzzy()
.withThreshold(.8f)
.withPrefixLength(1)
.onField("history")
.matching("starm")
.createQuery();
threshold
is the limit above which two terms
are considering matching. It's a decimal between 0 and 1 and defaults
to 0.5. prefixLength
is the length of the prefix
ignored by the "fuzzyness": while it defaults to 0, a non zero value
is recommended for indexes containing a huge amount of distinct
terms.
You can also execute wildcard queries (queries where some of
parts of the word are unknown). ?
represents a
single character and *
represents any character
sequence. Note that for performance purposes, it is recommended that
the query does not start with either ?
or
*
.
Query luceneQuery = mythQB
.keyword()
.wildcard()
.onField("history")
.matching("sto*")
.createQuery();
Wildcard queries do not apply the analyzer on the matching
terms. Otherwise the risk of *
or
?
being mangled is too high.
So far we have been looking for words or sets of words, you can
also search exact or approximate sentences. Use
phrase()
to do so.
Query luceneQuery = mythQB
.phrase()
.onField("history")
.sentence("Thou shalt not kill")
.createQuery();
You can search approximate sentences by adding a slop factor. The slop factor represents the number of other words permitted in the sentence: this works like a within or near operator
Query luceneQuery = mythQB
.phrase()
.withSlop(3)
.onField("history")
.sentence("Thou kill")
.createQuery();
After looking at all these query examples for searching for to a given word, it is time to introduce range queries (on numbers, dates, strings etc). A range query searches for a value in between given boundaries (included or not) or for a value below or above a given boundary (included or not).
//look for 0 <= starred < 3
Query luceneQuery = mythQB
.range()
.onField("starred")
.from(0).to(3).excludeLimit()
.createQuery();
//look for myths strictly BC
Date beforeChrist = ...;
Query luceneQuery = mythQB
.range()
.onField("creationDate")
.below(beforeChrist).excludeLimit()
.createQuery();
Finally, you can aggregate (combine) queries to create more complex queries. The following aggregation operators are available:
SHOULD
: the query query should contain
the matching elements of the subquery
MUST
: the query must contain the matching
elements of the subquery
MUST NOT
: the query must not contain the
matching elements of the subquery
The subqueries can be any Lucene query including a boolean query itself. Let's look at a few examples:
//look for popular modern myths that are not urban
Date twentiethCentury = ...;
Query luceneQuery = mythQB
.bool()
.must( mythQB.keyword().onField("description").matching("urban").createQuery() )
.not()
.must( mythQB.range().onField("starred").above(4).createQuery() )
.must( mythQB
.range()
.onField("creationDate")
.above(twentiethCentury)
.createQuery() )
.createQuery();
//look for popular myths that are preferably urban
Query luceneQuery = mythQB
.bool()
.should( mythQB.keyword().onField("description").matching("urban").createQuery() )
.must( mythQB.range().onField("starred").above(4).createQuery() )
.createQuery();
//look for all myths except religious ones
Query luceneQuery = mythQB
.all()
.except( monthQb
.keyword()
.onField( "description_stem" )
.matching( "religion" )
.createQuery()
)
.createQuery();
We already have seen several query options in the previous example, but lets summarize again the options for query types and fields:
boostedTo
(on query type and on
field): boost the whole query or the specific field to a given
factor
withConstantScore
(on query): all
results matching the query have a constant score equals to the
boost
filteredBy(Filter)
(on query):
filter query results using the Filter
instance
ignoreAnalyzer
(on field): ignore
the analyzer when processing this field
ignoreFieldBridge
(on field):
ignore field bridge when processing this field
Let's check out an example using some of these options
Query luceneQuery = mythQB
.bool()
.should( mythQB.keyword().onField("description").matching("urban").createQuery() )
.should( mythQB
.keyword()
.onField("name")
.boostedTo(3)
.ignoreAnalyzer()
.matching("urban").createQuery() )
.must( mythQB
.range()
.boostedTo(5).withConstantScore()
.onField("starred").above(4).createQuery() )
.createQuery();
As you can see, the Hibernate Search query DSL is an easy to use and easy to read query API and by accepting and producing Lucene queries, you can easily incorporate query types not (yet) supported by the DSL. Please give us feedback!
So far we only covered the process of how to create your Lucene query (see Section 5.1, “Building queries”). However, this is only the first step in the chain of actions. Let's now see how to build the Hibernate Search query from the Lucene query.
Once the Lucene query is built, it needs to be wrapped into an Hibernate Query. If not specified otherwise, the query will be executed against all indexed entities, potentially returning all types of indexed classes.
Example 5.4. Wrapping a Lucene query into a Hibernate Query
FullTextSession fullTextSession = Search.getFullTextSession( session );
org.hibernate.Query fullTextQuery = fullTextSession.createFullTextQuery( luceneQuery );
It is advised, from a performance point of view, to restrict the returned types:
Example 5.5. Filtering the search result by entity type
fullTextQuery = fullTextSession
.createFullTextQuery(luceneQuery, Customer.class);
// or
fullTextQuery = fullTextSession
.createFullTextQuery(luceneQuery, Item.class, Actor.class);
In Example 5.5, “Filtering the search result by entity type” the first
example returns only matching Customer
s, the
second returns matching Actor
s and
Item
s. The type restriction is fully
polymorphic which means that if there are two indexed subclasses
Salesman
and Customer
of
the baseclass Person
, it is possible to just
specify Person.class
in order to filter on
result types.
Out of performance reasons it is recommended to restrict the number of returned objects per query. In fact is a very common use case anyway that the user navigates from one page to an other. The way to define pagination is exactly the way you would define pagination in a plain HQL or Criteria query.
Example 5.6. Defining pagination for a search query
org.hibernate.Query fullTextQuery =
fullTextSession.createFullTextQuery(luceneQuery, Customer.class);
fullTextQuery.setFirstResult(15); //start from the 15th element
fullTextQuery.setMaxResults(10); //return 10 elements
It is still possible to get the total number of matching
elements regardless of the pagination via
fulltextQuery.
getResultSize()
Apache Lucene provides a very flexible and powerful way to sort results. While the default sorting (by relevance) is appropriate most of the time, it can be interesting to sort by one or several other properties. In order to do so set the Lucene Sort object to apply a Lucene sorting strategy.
Example 5.7. Specifying a Lucene Sort
in order to
sort the results
org.hibernate.search.FullTextQuery query = s.createFullTextQuery( query, Book.class );
org.apache.lucene.search.Sort sort = new Sort(
new SortField("title", SortField.STRING)); query.setSort(sort);
List results = query.list();
Be aware that fields used for sorting must not be tokenized (see Section 4.1.1.2, “@Field”).
When you restrict the return types to one class, Hibernate Search loads the objects using a single query. It also respects the static fetching strategy defined in your domain model.
It is often useful, however, to refine the fetching strategy for a specific use case.
Example 5.8. Specifying FetchMode
on a
query
Criteria criteria =
s.createCriteria(Book.class).setFetchMode("authors", FetchMode.JOIN);
s.createFullTextQuery(luceneQuery).setCriteriaQuery(criteria);
In this example, the query will return all Books matching the luceneQuery. The authors collection will be loaded from the same query using an SQL outer join.
When defining a criteria query, it is not necessary to restrict the returned entity types when creating the Hibernate Search query from the full text session: the type is guessed from the criteria query itself.
Only fetch mode can be adjusted, refrain from applying any
other restriction. While it is known to work as of Hibernate Search
4, using restriction (ie a where clause) on your
Criteria
query should be avoided when
possible. getResultSize()
will throw a
SearchException
if used in conjunction with a
Criteria
with restriction.
You cannot use setCriteriaQuery
if
more than one entity type is expected to be returned.
For some use cases, returning the domain object (including its associations) is overkill. Only a small subset of the properties is necessary. Hibernate Search allows you to return a subset of properties:
Example 5.9. Using projection instead of returning the full domain object
org.hibernate.search.FullTextQuery query =
s.createFullTextQuery(luceneQuery, Book.class);
query.setProjection("id", "summary", "body", "mainAuthor.name");
List results = query.list();
Object[] firstResult = (Object[]) results.get(0);
Integer id = firstResult[0];
String summary = firstResult[1];
String body = firstResult[2];
String authorName = firstResult[3];
Hibernate Search extracts the properties from the Lucene index
and convert them back to their object representation, returning a list
of Object[]
. Projections avoid a potential
database round trip (useful if the query response time is critical).
However, it also has several constraints:
the properties projected must be stored in the index
(@Field(store=Store.YES)
), which increases the
index size
the properties projected must use a
FieldBridge
implementing
org.hibernate.search.bridge.TwoWayFieldBridge
or
org.hibernate.search.bridge.TwoWayStringBridge
,
the latter being the simpler version.
All Hibernate Search built-in types are two-way.
you can only project simple properties of the indexed entity or its embedded associations. This means you cannot project a whole embedded entity.
projection does not work on collections or maps which are
indexed via @IndexedEmbedded
Projection is also useful for another kind of use case. Lucene can provide metadata information about the results. By using some special projection constants, the projection mechanism can retrieve this metadata:
Example 5.10. Using projection in order to retrieve meta data
org.hibernate.search.FullTextQuery query =
s.createFullTextQuery(luceneQuery, Book.class);
query.setProjection( FullTextQuery.SCORE, FullTextQuery.THIS, "mainAuthor.name" );
List results = query.list();
Object[] firstResult = (Object[]) results.get(0);
float score = firstResult[0];
Book book = firstResult[1];
String authorName = firstResult[2];
You can mix and match regular fields and projection constants. Here is the list of the available constants:
FullTextQuery.THIS
: returns the
initialized and managed entity (as a non projected query would
have done).
FullTextQuery.DOCUMENT
: returns the
Lucene Document related to the object projected.
FullTextQuery.OBJECT_CLASS
: returns
the class of the indexed entity.
FullTextQuery.SCORE
: returns the
document score in the query. Scores are handy to compare one
result against an other for a given query but are useless when
comparing the result of different queries.
FullTextQuery.ID
: the id property
value of the projected object.
FullTextQuery.DOCUMENT_ID
: the Lucene
document id. Careful, Lucene document id can change overtime
between two different IndexReader opening.
FullTextQuery.EXPLANATION
: returns
the Lucene Explanation object for the matching object/document in
the given query. Do not use if you retrieve a lot of data. Running
explanation typically is as costly as running the whole Lucene
query per matching element. Make sure you use projection!
By default, Hibernate Search uses the most appropriate strategy to initialize entities matching your full text query. It executes one (or several) queries to retrieve the required entities. This is the best approach to minimize database round trips in a scenario where none / few of the retrieved entities are present in the persistence context (ie the session) or the second level cache.
If most of your entities are present in the second level cache, you can force Hibernate Search to look into the cache before retrieving an object from the database.
Example 5.11. Check the second-level cache before using a query
FullTextQuery query = session.createFullTextQuery(luceneQuery, User.class);
query.initializeObjectWith(
ObjectLookupMethod.SECOND_LEVEL_CACHE,
DatabaseRetrievalMethod.QUERY
);
ObjectLookupMethod
defines the strategy
used to check if an object is easily accessible (without database
round trip). Other options are:
ObjectLookupMethod.PERSISTENCE_CONTEXT
:
useful if most of the matching entities are already in the
persistence context (ie loaded in the
Session
or
EntityManager
)
ObjectLookupMethod.SECOND_LEVEL_CACHE
:
check first the persistence context and then the second-level
cache.
Note that to search in the second-level cache, several settings must be in place:
the second level cache must be properly configured and active
the entity must have enabled second-level cache (eg via
@Cacheable
)
the Session
,
EntityManager
or
Query
must allow access to the
second-level cache for read access (ie
CacheMode.NORMAL
in Hibernate native APIs or
CacheRetrieveMode.USE
in JPA 2 APIs).
Avoid using
ObjectLookupMethod.SECOND_LEVEL_CACHE
unless your
second level cache implementation is either EHCache or Infinispan;
other second level cache providers don't currently implement this
operation efficiently.
You can also customize how objects are loaded from the database
(if not found before). Use
DatabaseRetrievalMethod
for that:
QUERY
(default): use a (set of)
queries to load several objects in batch. This is usually the best
approach.
FIND_BY_ID
: load objects one by one
using the
Session
.get
or
EntityManager
.find
semantic. This might be useful if batch-size is set on the entity
(in which case, entities will be loaded in batch by Hibernate
Core). QUERY
should be preferred almost all
the time.
You can limit the time a query takes in Hibernate Search in two ways:
raise an exception when the limit is reached
limit to the number of results retrieved when the time limit is raised
You can decide to stop a query if when it takes more than a
predefined amount of time. Note that this is a best effort basis but
if Hibernate Search still has significant work to do and if we are
beyond the time limit, a
QueryTimeoutException
will be raised
(org.hibernate.QueryTimeoutException
or
javax.persistence.QueryTimeoutException
depending on your programmatic API).
To define the limit when using the native Hibernate APIs, use one of the following approaches
Example 5.12. Defining a timeout in query execution
Query luceneQuery = ...;
FullTextQuery query = fullTextSession.createFullTextQuery(luceneQuery, User.class);
//define the timeout in seconds
query.setTimeout(5);
//alternatively, define the timeout in any given time unit
query.setTimeout(450, TimeUnit.MILLISECONDS);
try {
query.list();
}
catch (org.hibernate.QueryTimeoutException e) {
//do something, too slow
}
Likewise getResultSize()
,
iterate()
and
scroll()
honor the timeout but only until
the end of the method call. That simply means that the methods of
Iterable
or the
ScrollableResults
ignore the timeout.
explain()
does not honor the
timeout: this method is used for debug purposes and in particular
to find out why a query is slow
When using JPA, simply use the standard way of limiting query execution time.
Example 5.13. Defining a timeout in query execution
Query luceneQuery = ...;
FullTextQuery query = fullTextEM.createFullTextQuery(luceneQuery, User.class);
//define the timeout in milliseconds
query.setHint( "javax.persistence.query.timeout", 450 );
try {
query.getResultList();
}
catch (javax.persistence.QueryTimeoutException e) {
//do something, too slow
}
Remember, this is a best effort approach and does not guarantee to stop exactly on the specified timeout.
Alternatively, you can return the number of results which have already been fetched by the time the limit is reached. Note that only the Lucene part of the query is influenced by this limit. It is possible that, if you retrieve managed object, it takes longer to fetch these objects.
This approach is not compatible with the
setTimeout
approach.
To define this soft limit, use the following approach
Example 5.14. Defining a time limit in query execution
Query luceneQuery = ...;
FullTextQuery query = fullTextSession.createFullTextQuery(luceneQuery, User.class);
//define the timeout in seconds
query.limitExecutionTimeTo(500, TimeUnit.MILLISECONDS);
List results = query.list();
Likewise getResultSize()
,
iterate()
and
scroll()
honor the time limit but only
until the end of the method call. That simply means that the methods
of Iterable
or the
ScrollableResults
ignore the timeout.
You can determine if the results have been partially loaded by
invoking the hasPartialResults
method.
Example 5.15. Determines when a query returns partial results
Query luceneQuery = ...;
FullTextQuery query = fullTextSession.createFullTextQuery(luceneQuery, User.class);
//define the timeout in seconds
query.limitExecutionTimeTo(500, TimeUnit.MILLISECONDS);
List results = query.list();
if ( query.hasPartialResults() ) {
displayWarningToUser();
}
If you use the JPA API,
limitExecutionTimeTo
and
hasPartialResults
are also available to
you.
Once the Hibernate Search query is built, executing it is in no way
different than executing a HQL or Criteria query. The same paradigm and
object semantic applies. All the common operations are available:
list()
, uniqueResult()
,
iterate()
,
scroll()
.
If you expect a reasonable number of results (for example using
pagination) and expect to work on all of them,
list()
or
uniqueResult()
are recommended.
list()
work best if the entity
batch-size
is set up properly. Note that Hibernate
Search has to process all Lucene Hits elements (within the pagination)
when using list()
,
uniqueResult()
and
iterate()
.
If you wish to minimize Lucene document loading,
scroll()
is more appropriate. Don't forget to
close the ScrollableResults
object when you're
done, since it keeps Lucene resources. If you expect to use
scroll,
but wish to load objects in batch, you
can use query.setFetchSize()
. When an object is
accessed, and if not already loaded, Hibernate Search will load the next
fetchSize
objects in one pass.
Pagination is preferred over scrolling.
It is sometimes useful to know the total number of matching documents:
for the Google-like feature "1-10 of about 888,000,000"
to implement a fast pagination navigation
to implement a multi step search engine (adding approximation if the restricted query return no or not enough results)
Of course it would be too costly to retrieve all the matching documents. Hibernate Search allows you to retrieve the total number of matching documents regardless of the pagination parameters. Even more interesting, you can retrieve the number of matching elements without triggering a single object load.
Example 5.16. Determining the result size of a query
org.hibernate.search.FullTextQuery query =
s.createFullTextQuery(luceneQuery, Book.class);
//return the number of matching books without loading a single one
assert 3245 == query.getResultSize();
org.hibernate.search.FullTextQuery query =
s.createFullTextQuery(luceneQuery, Book.class);
query.setMaxResult(10);
List results = query.list();
//return the total number of matching books regardless of pagination
assert 3245 == query.getResultSize();
Like Google, the number of results is an approximation if the index is not fully up-to-date with the database (asynchronous cluster for example).
As seen in Section 5.1.3.5, “Projection” projection results are
returns as Object
arrays. This data structure is
not always matching the application needs. In this cases It is possible
to apply a ResultTransformer
which post query
execution can build the needed data structure:
Example 5.17. Using ResultTransformer in conjunction with projections
org.hibernate.search.FullTextQuery query =
s.createFullTextQuery(luceneQuery, Book.class);
query.setProjection("title", "mainAuthor.name"); query.setResultTransformer( new StaticAliasToBeanResultTransformer( BookView.class, "title", "author" ) );
List<BookView> results = (List<BookView>) query.list();
for (BookView view : results) {
log.info("Book: " + view.getTitle() + ", " + view.getAuthor());
}
Examples of ResultTransformer
implementations can be found in the Hibernate Core codebase.
You will find yourself sometimes puzzled by a result showing up in
a query or a result not showing up in a query. Luke is a great tool to
understand those mysteries. However, Hibernate Search also gives you
access to the Lucene Explanation
object for a
given result (in a given query). This class is considered fairly
advanced to Lucene users but can provide a good understanding of the
scoring of an object. You have two ways to access the Explanation object
for a given result:
Use the fullTextQuery.explain(int)
method
Use projection
The first approach takes a document id as a parameter and return
the Explanation object. The document id can be retrieved using
projection and the FullTextQuery.DOCUMENT_ID
constant.
The Document id has nothing to do with the entity id. Do not mess up these two notions.
In the second approach you project the
Explanation
object using the
FullTextQuery.EXPLANATION
constant.
Example 5.18. Retrieving the Lucene Explanation object using projection
FullTextQuery ftQuery = s.createFullTextQuery( luceneQuery, Dvd.class )
.setProjection(
FullTextQuery.DOCUMENT_ID,
FullTextQuery.EXPLANATION,
FullTextQuery.THIS );
@SuppressWarnings("unchecked") List<Object[]> results = ftQuery.list();
for (Object[] result : results) {
Explanation e = (Explanation) result[1];
display( e.toString() );
}
Be careful, building the explanation object is quite expensive, it is roughly as expensive as running the Lucene query again. Don't do it if you don't need the object
Apache Lucene has a powerful feature that allows to filter query results according to a custom filtering process. This is a very powerful way to apply additional data restrictions, especially since filters can be cached and reused. Some interesting use cases are:
security
temporal data (eg. view only last month's data)
population filter (eg. search limited to a given category)
and many more
Hibernate Search pushes the concept further by introducing the notion of parameterizable named filters which are transparently cached. For people familiar with the notion of Hibernate Core filters, the API is very similar:
Example 5.19. Enabling fulltext filters for a given query
fullTextQuery = s.createFullTextQuery(query, Driver.class);
fullTextQuery.enableFullTextFilter("bestDriver");
fullTextQuery.enableFullTextFilter("security").setParameter("login", "andre");
fullTextQuery.list(); //returns only best drivers where andre has credentials
In this example we enabled two filters on top of the query. You can enable (or disable) as many filters as you like.
Declaring filters is done through the
@FullTextFilterDef
annotation. This annotation can
be on any @Indexed
entity regardless of the query the
filter is later applied to. This implies that filter definitions are
global and their names must be unique. A
SearchException
is thrown in case two different
@FullTextFilterDef
annotations with the same name
are defined. Each named filter has to specify its actual filter
implementation.
Example 5.20. Defining and implementing a Filter
@Entity @Indexed @FullTextFilterDefs( { @FullTextFilterDef(name = "bestDriver", impl = BestDriversFilter.class), @FullTextFilterDef(name = "security", impl = SecurityFilterFactory.class) }) public class Driver { ... }
public class BestDriversFilter extends org.apache.lucene.search.Filter {
public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
OpenBitSet bitSet = new OpenBitSet( reader.maxDoc() );
TermDocs termDocs = reader.termDocs( new Term( "score", "5" ) );
while ( termDocs.next() ) {
bitSet.set( termDocs.doc() );
}
return bitSet;
}
}
BestDriversFilter
is an example of a simple
Lucene filter which reduces the result set to drivers whose score is 5. In
this example the specified filter implements the
org.apache.lucene.search.Filter
directly and contains a
no-arg constructor.
If your Filter creation requires additional steps or if the filter you want to use does not have a no-arg constructor, you can use the factory pattern:
Example 5.21. Creating a filter using the factory pattern
@Entity
@Indexed
@FullTextFilterDef(name = "bestDriver", impl = BestDriversFilterFactory.class)
public class Driver { ... }
public class BestDriversFilterFactory {
@Factory
public Filter getFilter() {
//some additional steps to cache the filter results per IndexReader
Filter bestDriversFilter = new BestDriversFilter();
return new CachingWrapperFilter(bestDriversFilter);
}
}
Hibernate Search will look for a @Factory
annotated method and use it to build the filter instance. The factory must
have a no-arg constructor.
Named filters come in handy where parameters have to be passed to the filter. For example a security filter might want to know which security level you want to apply:
Example 5.22. Passing parameters to a defined filter
fullTextQuery = s.createFullTextQuery(query, Driver.class);
fullTextQuery.enableFullTextFilter("security").setParameter("level", 5);
Each parameter name should have an associated setter on either the filter or filter factory of the targeted named filter definition.
Example 5.23. Using parameters in the actual filter implementation
public class SecurityFilterFactory {
private Integer level;
/**
* injected parameter
*/
public void setLevel(Integer level) {
this.level = level;
}
@Key public FilterKey getKey() {
StandardFilterKey key = new StandardFilterKey();
key.addParameter( level );
return key;
}
@Factory
public Filter getFilter() {
Query query = new TermQuery( new Term("level", level.toString() ) );
return new CachingWrapperFilter( new QueryWrapperFilter(query) );
}
}
Note the method annotated @Key
returning a
FilterKey
object. The returned object has a special
contract: the key object must implement equals()
/ hashCode()
so that 2 keys are equal if and only
if the given Filter
types are the same and the set
of parameters are the same. In other words, 2 filter keys are equal if and
only if the filters from which the keys are generated can be interchanged.
The key object is used as a key in the cache mechanism.
@Key
methods are needed only if:
you enabled the filter caching system (enabled by default)
your filter has parameters
In most cases, using the StandardFilterKey
implementation will be good enough. It delegates the
equals()
/ hashCode()
implementation to each of the parameters equals and hashcode
methods.
As mentioned before the defined filters are per default cached and
the cache uses a combination of hard and soft references to allow disposal
of memory when needed. The hard reference cache keeps track of the most
recently used filters and transforms the ones least used to
SoftReferences
when needed. Once the limit of the
hard reference cache is reached additional filters are cached as
SoftReferences
. To adjust the size of the hard
reference cache, use
hibernate.search.filter.cache_strategy.size
(defaults
to 128). For advanced use of filter caching, you can implement your own
FilterCachingStrategy
. The classname is defined by
hibernate.search.filter.cache_strategy
.
This filter caching mechanism should not be confused with caching
the actual filter results. In Lucene it is common practice to wrap filters
using the IndexReader
around a
CachingWrapperFilter.
The wrapper will cache the
DocIdSet
returned from the
getDocIdSet(IndexReader reader)
method to avoid
expensive recomputation. It is important to mention that the computed
DocIdSet
is only cachable for the same
IndexReader
instance, because the reader
effectively represents the state of the index at the moment it was opened.
The document list cannot change within an opened
IndexReader
. A different/new
IndexReader
instance, however, works potentially on a
different set of Document
s (either from a different
index or simply because the index has changed), hence the cached
DocIdSet
has to be recomputed.
Hibernate Search also helps with this aspect of caching. Per default
the cache
flag of @FullTextFilterDef
is set to
FilterCacheModeType.INSTANCE_AND_DOCIDSETRESULTS
which
will automatically cache the filter instance as well as wrap the specified
filter around a Hibernate specific implementation of
CachingWrapperFilter
. In contrast to Lucene's
version of this class SoftReference
s are used
together with a hard reference count (see discussion about filter cache).
The hard reference count can be adjusted using
hibernate.search.filter.cache_docidresults.size
(defaults to 5). The wrapping behaviour can be controlled using the
@FullTextFilterDef.cache
parameter. There are three
different values for this parameter:
Value | Definition |
---|---|
FilterCacheModeType.NONE | No filter instance and no result is cached by Hibernate Search. For every filter call, a new filter instance is created. This setting might be useful for rapidly changing data sets or heavily memory constrained environments. |
FilterCacheModeType.INSTANCE_ONLY | The filter instance is cached and reused across
concurrent Filter.getDocIdSet() calls.
DocIdSet results are not cached. This
setting is useful when a filter uses its own specific caching
mechanism or the filter results change dynamically due to
application specific events making
DocIdSet caching in both cases
unnecessary. |
FilterCacheModeType.INSTANCE_AND_DOCIDSETRESULTS | Both the filter instance and the
DocIdSet results are cached. This is the
default value. |
Last but not least - why should filters be cached? There are two areas where filter caching shines:
the system does not update the targeted entity index often (in other words, the IndexReader is reused a lot)
the Filter's DocIdSet is expensive to compute (compared to the time spent to execute the query)
It is possible, in a sharded environment to execute queries on a subset of the available shards. This can be done in two steps:
create a sharding strategy that does select a subset of
IndexManager
s depending on some filter
configuration
activate the proper filter at query time
Let's first look at an example of sharding strategy that query on a specific customer shard if the customer filter is activated.
public class CustomerShardingStrategy implements IndexShardingStrategy {
// stored IndexManagers in a array indexed by customerID
private IndexManager[] indexManagers;
public void initialize(Properties properties, IndexManager[] indexManagers) {
this.indexManagers = indexManagers;
}
public IndexManager[] getIndexManagersForAllShards() {
return indexManagers;
}
public IndexManager getIndexManagerForAddition(
Class<?> entity, Serializable id, String idInString, Document document) {
Integer customerID = Integer.parseInt(document.getFieldable("customerID").stringValue());
return indexManagers[customerID];
}
public IndexManager[] getIndexManagersForDeletion(
Class<?> entity, Serializable id, String idInString) {
return getIndexManagersForAllShards();
}
/**
* Optimization; don't search ALL shards and union the results; in this case, we
* can be certain that all the data for a particular customer Filter is in a single
* shard; simply return that shard by customerID.
*/
public IndexManager[] getIndexManagersForQuery(
FullTextFilterImplementor[] filters) {
FullTextFilter filter = getCustomerFilter(filters, "customer");
if (filter == null) {
return getIndexManagersForAllShards();
}
else {
return new IndexManager[] { indexManagers[Integer.parseInt(
filter.getParameter("customerID").toString())] };
}
}
private FullTextFilter getCustomerFilter(FullTextFilterImplementor[] filters, String name) {
for (FullTextFilterImplementor filter: filters) {
if (filter.getName().equals(name)) return filter;
}
return null;
}
}
In this example, if the filter named customer
is present, we make sure to only use the shard dedicated to this
customer. Otherwise, we return all shards. A given Sharding strategy can
react to one or more filters and depends on their parameters.
The second step is simply to activate the filter at query time.
While the filter can be a regular filter (as defined in Section 5.3, “Filters”) which also filters Lucene results after the
query, you can make use of a special filter that will only be passed to
the sharding strategy and otherwise ignored for the rest of the query.
Simply use the ShardSensitiveOnlyFilter
class
when declaring your filter.
@Entity @Indexed @FullTextFilterDef(name="customer", impl=ShardSensitiveOnlyFilter.class)
public class Customer {
...
}
FullTextQuery query = ftEm.createFullTextQuery(luceneQuery, Customer.class); query.enableFulltextFilter("customer").setParameter("CustomerID", 5);
@SuppressWarnings("unchecked")
List<Customer> results = query.getResultList();
Note that by using the
ShardSensitiveOnlyFilter
, you do not have to
implement any Lucene filter. Using filters and sharding strategy
reacting to these filters is recommended to speed up queries in a
sharded environment.
Faceted search is a technique which allows to divide the results of a query into multiple categories. This categorization includes the calculation of hit counts for each category and the ability to further restrict search results based on these facets (categories). Example 5.24, “Search for 'Hibernate Search' on Amazon” shows a faceting example. The search for 'Hibernate Search' results in fifteen hits which are displayed on the main part of the page. The navigation bar on the left, however, shows the category Computers & Internet with its subcategories Programming, Computer Science, Databases, Software, Web Development, Networking and Home Computing. For each of these subcategories the number of books is shown matching the main search criteria and belonging to the respective subcategory. This division of the category Computers & Internet is one facet of this search. Another one is for example the average customer review rating.
In Hibernate Search the classes QueryBuilder
and FullTextQuery
are the entry point to the
faceting API. The former allows to create faceting requests whereas the
latter gives access to the so called FacetManager
.
With the help of the FacetManager
faceting requests
can be applied on a query and selected facets can be added to an existing
query in order to refine search results. The following sections will
describe the faceting process in more detail. The examples will use the
entity Cd
as shown in Example 5.25, “Example entity for faceting”:
Example 5.25. Example entity for faceting
@Entity
@Indexed
public class Cd {
@Id
@GeneratedValue
private int id;
@Fields( {
@Field,
@Field(name = "name_un_analyzed", analyze = Analyze.NO)
})
private String name;
@Field(analyze = Analyze.NO)
private int price;
Field(analyze = Analyze.NO)
@DateBridge(resolution = Resolution.YEAR)
private Date releaseYear;
@Field(analyze = Analyze.NO)
private String label;
// setter/getter
...
The first step towards a faceted search is to create the
FacetingRequest
. Currently two types of faceting
requests are supported. The first type is called discrete
faceting and the second type range
faceting request.
In the case of a discrete faceting request you start with giving
the request a unique name. This name will later be used to retrieve
the facet values (see Section 5.4.4, “Interpreting a Facet
result”). Then you need to
specify on which index field you want to categorize on and which
faceting options to apply. An example for a discrete faceting request
can be seen in Example 5.26, “Creating a discrete faceting request”:
Example 5.26. Creating a discrete faceting request
QueryBuilder builder = fullTextSession.getSearchFactory()
.buildQueryBuilder()
.forEntity(Cd.class)
.get();
FacetingRequest labelFacetingRequest = builder.facet()
.name("labelFacetRequest")
.onField("label")
.discrete()
.orderedBy(FacetSortOrder.COUNT_DESC)
.includeZeroCounts(false)
.maxFacetCount(3)
.createFacetingRequest();
When executing this faceting request a
Facet
instance will be created for each
discrete value for the indexed field label
. The
Facet
instance will record the actual field
value including how often this particular field value occurs within
the original query results. Parameters orderedBy
,
includeZeroCounts
and
maxFacetCount
are optional and can be applied
on any faceting request.
Parameter orderedBy
allows to specify in which
order the created facets will be returned. The default is
FacetSortOrder.COUNT_DESC
, but you can also sort
on the field value. Parameter includeZeroCount
determines whether facets with a count of 0 will be included in the
result (by default they are) and maxFacetCount
allows to limit the maximum amount of facets returned.
There are several preconditions an indexed field has to meet
in order to categorize (facet) on it. The indexed
property must be of type String
,
Date
or a subtype of
Number
; also null
values
should be avoided. Finally the property has to be indexed with
Analyze.NO
and you can not use it in combination
with @NumericField
. When you need these other
options we suggest to index the property twice and use the appropriate
field depending on the use case:
... @Fields({ @Field( name="price" ), @Field( name="price_facet", analyze=Analyze.NO ) }) @NumericFields({ @NumericField( forField="price" ) }) private int price; ...
The creation of a range faceting request is similar. We also
start with a name for the request and the field to facet on. Then
we have to specify ranges for the field values. A range faceting
request can be seen in Example 5.27, “Creating a range faceting request”.
There, three different price ranges are specified.
below
and above
can
only be specified once, but you can specify as many
from
- to
ranges as
you want. For each range boundary you can also specify via
excludeLimit
whether it is included into the
range or not.
Example 5.27. Creating a range faceting request
QueryBuilder builder = fullTextSession.getSearchFactory()
.buildQueryBuilder()
.forEntity(Cd.class)
.get();
FacetingRequest priceFacetingRequest = builder.facet()
.name("priceFaceting")
.onField("price_facet")
.range()
.below(1000)
.from(1001).to(1500)
.above(1500).excludeLimit()
.createFacetingRequest();
The result of applying a faceting request is a list of
Facet
instances as seen in Example 5.28, “Applying a faceting request”. The order within the list is
given by the FacetSortOrder
parameter specified
via orderedBy
when creating the faceting
request. The default value is
FacetSortOrder.COUNT_DESC
, meaning facets are
ordered by their count in descending order (highest count first).
Other values are COUNT_ASC
,
FIELD_VALUE
and
RANGE_DEFINITION_ORDER
.
COUNT_ASC
returns the facets in ascending count
order whereas FIELD_VALUE
will return them in
alphabetical order of the facet/category value (see Section 5.4.4, “Interpreting a Facet
result”).
RANGE_DEFINITION_ORDER
only applies for range
faceting request and returns the facets in the same order in which the
ranges are defined. For Example 5.27, “Creating a range faceting request” this
would mean the facet for the range of below 1000 would be returned
first, followed by the facet for the range 1001 to 1500 and finally
the facet for above 1500.
In Section 5.4.1, “Creating a faceting request” we have
seen how to create a faceting request. Now it is time to apply it on a
query. The key is the FacetManager
which can be
retrieved via the FullTextQuery
(see Example 5.28, “Applying a faceting request”).
Example 5.28. Applying a faceting request
// create a fulltext query
Query luceneQuery = builder.all().createQuery(); // match all query
FullTextQuery fullTextQuery = fullTextSession.createFullTextQuery(luceneQuery, Cd.class);
// retrieve facet manager and apply faceting request
FacetManager facetManager = fullTextQuery.getFacetManager();
facetManager.enableFaceting(priceFacetingRequest);
// get the list of Cds
List<Cd> cds = fullTextQuery.list();
...
// retrieve the faceting results
List<Facet> facets = facetManager.getFacets("priceFaceting");
...
You need to enable the faceting request before you execute the
query. You do that via
facetManager.enableFaceting(<facetName>)
.
You can enable as many faceting requests as you like, then you execute
the query and retrieve the facet results for a given request via
facetManager.getFacets(<facetname>)
. For
each request you will get a list of Facet
instances. Facet requests stay active and get applied to the fulltext
query until they are either explicitly disabled via
disableFaceting(<facetName>)
or the
query is discarded.
Each facet request results in a list of
Facet
instances. Each instance represents one
facet/category value. In the CD example (Example 5.26, “Creating a discrete faceting request”) where we want to categorize on
the Cd labels, there would for example be a Facet
for each of the record labels Universal, Sony and Warner. Example 5.29, “Facet API” shows the API of
Facet
.
Example 5.29. Facet API
public interface Facet {
/**
* @return the faceting name this {@code Facet} belongs to.
*
* @see org.hibernate.search.query.facet.FacetingRequest#getFacetingName()
*/
String getFacetingName();
/**
* Return the {@code Document} field name this facet is targeting.
* The field needs to be indexed with {@code Analyze.NO}.
*
* @return the {@code Document} field name this facet is targeting.
*/
String getFieldName();
/**
* @return the value of this facet. In case of a discrete facet it is the actual
* {@code Document} field value. In case of a range query the value is a
* string representation of the range.
*/
String getValue();
/**
* @return the facet count.
*/
int getCount();
/**
* @return a Lucene {@link Query} which can be executed to retrieve all
* documents matching the value of this facet.
*/
Query getFacetQuery();
}
getFacetingName()
and
getFieldName()
are returning the facet request
name and the targeted document field name as specified by the underlying
FacetRequest
. For Example 5.26, “Creating a discrete faceting request” that would be
labelFacetRequest
and label
respectively. The interesting information is provided by
getValue()
and
getCount()
. The former is the actual
facet/category value, for example a concrete record label like
Universal. The latter returns the count for this value. To stick with
the example again, the count value tells you how many Cds are released
under the Universal label. Last but not least,
getFacetQuery()
returns a Lucene query which can
be used to retrieve the entities counted in this facet.
A common use case for faceting is a "drill-down" functionality
which allows you to narrow your original search by applying a given
facet on it. To do this, you can apply any of the returned
Facet
s as additional criteria on your original
query via FacetSelection
.
FacetSelection
s are available via the
FacetManager
and allow you to select a facet as
query criteria (selectFacets
), remove a facet
restriction (deselectFacets
), remove all facet
restrictions (clearSelectedFacets
) and retrieve
all currently selected facets
(getSelectedFacets
). Example 5.30, “Restricting query results via the application of a
FacetSelection
” shows an example.
Example 5.30. Restricting query results via the application of a
FacetSelection
// create a fulltext query
Query luceneQuery = builder.all().createQuery(); // match all query
FullTextQuery fullTextQuery = fullTextSession.createFullTextQuery( luceneQuery, clazz );
// retrieve facet manager and apply faceting request
FacetManager facetManager = fullTextQuery.getFacetManager();
facetManager.enableFaceting( priceFacetingRequest );
// get the list of Cd
List<Cd> cds = fullTextQuery.list();
assertTrue(cds.size() == 10);
// retrieve the faceting results
List<Facet> facets = facetManager.getFacets( "priceFaceting" );
assertTrue(facets.get(0).getCount() == 2)
// apply first facet as additional search criteria
FacetSelection facetSelection = facetManager.getFacetGroup( "priceFaceting" );
facetSelection.selectFacets( facets.get( 0 ) );
// re-execute the query
cds = fullTextQuery.list();
assertTrue(cds.size() == 2);
Query performance depends on several criteria:
the Lucene query itself: read the literature on this subject.
the number of loaded objects: use pagination and / or index projection (if needed).
the way Hibernate Search interacts with the Lucene readers: defines the appropriate Reader strategy.
caching frequently extracted values from the index: see Section 5.5.1, “Caching index values: FieldCache”.
The primary function of a Lucene index is to identify matches to your queries, still after the query is performed the results must be analyzed to extract useful information: typically Hibernate Search might need to extract the Class type and the primary key.
Extracting the needed values from the index has a performance cost, which in some cases might be very low and not noticeable, but in some other cases might be a good candidate for caching.
What is exactly needed depends on the kind of Projections being used (see Section 5.1.3.5, “Projection”), and in some cases the Class type is not needed as it can be inferred from the query context or other means.
Using the @CacheFromIndex
annotation you
can experiment different kinds of caching of the main metadata fields
required by Hibernate Search:
import static org.hibernate.search.annotations.FieldCacheType.CLASS;
import static org.hibernate.search.annotations.FieldCacheType.ID;
@Indexed
@CacheFromIndex( { CLASS, ID } )
public class Essay {
...
It is currently possible to cache Class types and IDs using this annotation:
CLASS
: Hibernate Search will use a Lucene
FieldCache to improve peformance of the Class type extraction from
the index.
This value is enabled by default, and is what Hibernate Search
will apply if you don't specify the
@CacheFromIndex
annotation.
ID
: Extracting the primary identifier
will use a cache. This is likely providing the best performing
queries, but will consume much more memory which in turn might
reduce performance.
Measure the performance and memory consumption impact after warmup (executing some queries): enabling Field Caches is likely to improve performance but this is not always the case.
Using a FieldCache has two downsides to consider:
Memory usage: these caches can be quite memory hungry. Typically the CLASS cache has lower requirements than the ID cache.
Index warmup: when using field caches, the first query on a new index or segment will be slower than when you don't have caching enabled.
With some queries the classtype won't be needed at all, in that
case even if you enabled the CLASS
field cache,
this might not be used; for example if you are targeting a single class,
obviously all returned values will be of that type (this is evaluated at
each Query execution).
For the ID FieldCache to be used, the ids of targeted entities
must be using a TwoWayFieldBridge
(as all
builting bridges), and all types being loaded in a specific query must
use the fieldname for the id, and have ids of the same type (this is
evaluated at each Query execution).
As Hibernate core applies changes to the Database, Hibernate Search detects these changes and will update the index automatically (unless the EventListeners are disabled). Sometimes changes are made to the database without using Hibernate, as when backup is restored or your data is otherwise affected; for these cases Hibernate Search exposes the Manual Index APIs to explicitly update or remove a single entity from the index, or rebuild the index for the whole database, or remove all references to a specific type.
All these methods affect the Lucene Index only, no changes are applied to the Database.
Using FullTextSession
.index(T
entity)
you can directly add or update a specific object
instance to the index. If this entity was already indexed, then the index
will be updated. Changes to the index are only applied at transaction
commit.
Example 6.1. Indexing an entity via FullTextSession.index(T
entity)
FullTextSession fullTextSession = Search.getFullTextSession(session);
Transaction tx = fullTextSession.beginTransaction();
Object customer = fullTextSession.load( Customer.class, 8 ); fullTextSession.index(customer);
tx.commit(); //index only updated at commit time
In case you want to add all instances for a type, or for all indexed
types, the recommended approach is to use a
MassIndexer
: see Section 6.3.2, “Using a MassIndexer” for more details.
The method FullTextSession.index(T
entity)
is considered an explicit indexing operation, so any
registered EntityIndexingInterceptor
won't be applied
in this case. For more information on EntityIndexingInterceptor
see Section 4.5, “Conditional indexing: to index or not based on entity state”.
It is equally possible to remove an entity or all entities of a
given type from a Lucene index without the need to physically remove them
from the database. This operation is named purging and is also done
through the FullTextSession
.
Example 6.2. Purging a specific instance of an entity from the index
FullTextSession fullTextSession = Search.getFullTextSession(session);
Transaction tx = fullTextSession.beginTransaction();
for (Customer customer : customers) {
fullTextSession.purge( Customer.class, customer.getId() );
}
tx.commit(); //index is updated at commit time
Purging will remove the entity with the given id from the Lucene index but will not touch the database.
If you need to remove all entities of a given type, you can use the
purgeAll
method. This operation removes all
entities of the type passed as a parameter as well as all its
subtypes.
Example 6.3. Purging all instances of an entity from the index
FullTextSession fullTextSession = Search.getFullTextSession(session);
Transaction tx = fullTextSession.beginTransaction(); fullTextSession.purgeAll( Customer.class );
//optionally optimize the index
//fullTextSession.getSearchFactory().optimize( Customer.class );
tx.commit(); //index changes are applied at commit time
As in the previous example, it is suggested to optimize the index after many purge operation to actually free the used space.
As is the case with method FullTextSession.index(T
entity)
, also purge
and
purgeAll
are considered explicit indexinging
operations: any registered EntityIndexingInterceptor
won't be applied. For more information on EntityIndexingInterceptor
see Section 4.5, “Conditional indexing: to index or not based on entity state”.
Methods index
,
purge
and purgeAll
are
available on FullTextEntityManager
as
well.
All manual indexing methods (index
,
purge
and purgeAll
)
only affect the index, not the database, nevertheless they are
transactional and as such they won't be applied until the transaction is
successfully committed, or you make use of
flushToIndexes
.
If you change the entity mapping to the index, chances are that the whole Index needs to be updated; For example if you decide to index a an existing field using a different analyzer you'll need to rebuild the index for affected types. Also if the Database is replaced (like restored from a backup, imported from a legacy system) you'll want to be able to rebuild the index from existing data. Hibernate Search provides two main strategies to choose from:
Using
FullTextSession
.flushToIndexes()
periodically, while using
FullTextSession
.index()
on all entities.
Use a MassIndexer
.
This strategy consists in removing the existing index and then
adding all entities back to the index using
FullTextSession
.purgeAll()
and
FullTextSession
.index()
,
however there are some memory and efficiency contraints. For maximum
efficiency Hibernate Search batches index operations and executes them
at commit time. If you expect to index a lot of data you need to be
careful about memory consumption since all documents are kept in a queue
until the transaction commit. You can potentially face an
OutOfMemoryException
if you don't empty the queue
periodically: to do this you can use
fullTextSession.flushToIndexes()
. Every time
fullTextSession.flushToIndexes()
is called (or
if the transaction is committed), the batch queue is processed applying
all index changes. Be aware that, once flushed, the changes cannot be
rolled back.
Example 6.4. Index rebuilding using index() and flushToIndexes()
fullTextSession.setFlushMode(FlushMode.MANUAL);
fullTextSession.setCacheMode(CacheMode.IGNORE);
transaction = fullTextSession.beginTransaction();
//Scrollable results will avoid loading too many objects in memory
ScrollableResults results = fullTextSession.createCriteria( Email.class )
.setFetchSize(BATCH_SIZE)
.scroll( ScrollMode.FORWARD_ONLY );
int index = 0;
while( results.next() ) {
index++;
fullTextSession.index( results.get(0) ); //index each element
if (index % BATCH_SIZE == 0) {
fullTextSession.flushToIndexes(); //apply changes to indexes
fullTextSession.clear(); //free memory since the queue is processed
}
}
transaction.commit();
Try to use a batch size that guarantees that your application will not run out of memory: with a bigger batch size objects are fetched faster from database but more memory is needed.
Hibernate Search's MassIndexer
uses several
parallel threads to rebuild the index; you can optionally select which
entities need to be reloaded or have it reindex all entities. This
approach is optimized for best performance but requires to set the
application in maintenance mode: making queries to the index is not
recommended when a MassIndexer is busy.
This will rebuild the index, deleting it and then reloading all entities from the database. Although it's simple to use, some tweaking is recommended to speed up the process: there are several parameters configurable.
During the progress of a MassIndexer the content of the index is undefined! If a query is performed while the MassIndexer is working most likely some results will be missing.
Example 6.6. Using a tuned MassIndexer
fullTextSession
.createIndexer( User.class )
.batchSizeToLoadObjects( 25 )
.cacheMode( CacheMode.NORMAL )
.threadsToLoadObjects( 12 )
.idFetchSize( 150 )
.progressMonitor( monitor ) //a MassIndexerProgressMonitor implementation
.startAndWait();
This will rebuild the index of all User instances (and subtypes),
and will create 12 parallel threads to load the User instances using
batches of 25 objects per query; these same 12 threads will also need
to process indexed embedded relations and custom FieldBridge
s
or ClassBridge
s, to finally output a Lucene
document. In this conversion process these threads are likely going to
need to trigger lazyloading of additional attributes, so you will
probably need a high number of threads working in parallel.
The number of threads working on actual index writing is defined by the backend
configuration of each index. See the option
worker.thread_pool.size
in Table 3.3, “Execution configuration”.
As of Hibernate Search 4.4.0, instead of indexing all the types
in parallel, the MassIndexer is configured by default to index only
one type in parallel. It prevents resource exhaustion especially
database connections and usually does not slow down the indexing.
You can however configure this behavior using
MassIndexer
.typesToIndexInParallel(int threadsToIndexObjects)
:
Example 6.7. Configuring the MassIndexer to index several types in parallel
fullTextSession
.createIndexer( User.class, Customer.class )
.typesToIndexInParallel( 2 )
.batchSizeToLoadObjects( 25 )
.cacheMode( CacheMode.NORMAL )
.threadsToLoadObjects( 5 )
.idFetchSize( 150 )
.progressMonitor( monitor ) //a MassIndexerProgressMonitor implementation
.startAndWait();
Generally we suggest to leave cacheMode to
CacheMode.IGNORE
(the default), as in most reindexing
situations the cache will be a useless additional overhead; it might be
useful to enable some other CacheMode
depending on
your data: it could increase performance if the main entity is relating
to enum-like data included in the index.
The MassIndexer was designed for speed and is unaware of transactions, so there is no need to begin one or committing. Also because it is not transactional it is not recommended to let users use the system during its processing, as it is unlikely people will be able to find results and the system load might be too high anyway.
The MassIndexer was designed to finish the reindexing task as quickly as possible, but this requires a bit of care in its configuration to behave fairly with your server resources.
There is a simple formula to understand how the different options applied to the MassIndexer affect the number of used worker threads and connections: each thread will require a JDBC connection.
threads = typesToIndexInParallel * (threadsToLoadObjects + 1); required JDBC connections = threads;
Let's see some suggestions for a roughly sane tuning starting point:
Option typesToIndexInParallel
should probably be a low value, like 1 or 2, depending on how
much of your CPUs have spare cycles and how slow a database round trip will be.
Before tuning a parallel run, experiment with options to tune your primary indexed entities in isolation.
Making threadsToLoadObjects
higher increases the preloading rate for the picked entities
from the database, but also increases memory usage and the pressure on the threads working on subsequent indexing.
Increasing parallelism usually helps as the bottleneck usually is the latency to the database connection: it's probably worth it to experiment with values significantly higher than the number of actual cores available, but make sure your database can handle all the multiple requests.
This advice might not apply to you: always measure the effects! We're providing this as a means to help you understand how these options are related.
Running the MassIndexer with many threads will require many connections to the database. If you don't have a sufficiently large connection pool, the MassIndexer itself and/or your other applications could starve being unable to serve other requests: make sure you size your connection pool accordingly to the options as explained in the above paragraph.
The "sweet spot" of number of threads to achieve best performance is highly dependent on your overall architecture, database design and even data values. All internal thread groups have meaningful names so they should be easily identified with most diagnostic tools, including simply threaddumps.
The provided MassIndexer is quite general purpose, and while we believe
it's a robust approach, you might be able to squeeze some better performance
by writing a custom implementation. To run your own MassIndexer
instead of using the one shipped with Hibernate Search you have to:
create an implementation of the org.hibernate.search.spi.MassIndexerFactory
interface;
set the property hibernate.search.massindexer.factoryclass
with the qualified class name of the factory implementation.
Example 6.8. Custom MassIndexerFactory
example
package org.myproject
import org.hibernate.search.spi.MassIndexerFactory
[...]
public class CustomIndexerFactory implements MassIndexerFactory {
public void initialize(Properties properties) {
}
public MassIndexer createMassIndexer(...) {
return new CustomIndexer();
}
}
hibernate.search.massindexer.factoryclass = org.myproject.CustomIndexerFactory
Other parameters which affect indexing time and memory consumption are:
hibernate.search.[default|<indexname>].exclusive_index_use
hibernate.search.[default|<indexname>].indexwriter.max_buffered_docs
hibernate.search.[default|<indexname>].indexwriter.max_merge_docs
hibernate.search.[default|<indexname>].indexwriter.merge_factor
hibernate.search.[default|<indexname>].indexwriter.merge_min_size
hibernate.search.[default|<indexname>].indexwriter.merge_max_size
hibernate.search.[default|<indexname>].indexwriter.merge_max_optimize_size
hibernate.search.[default|<indexname>].indexwriter.merge_calibrate_by_deletes
hibernate.search.[default|<indexname>].indexwriter.ram_buffer_size
hibernate.search.[default|<indexname>].indexwriter.term_index_interval
Previous versions also had a max_field_length
but
this was removed from Lucene, it's possible to obtain a similar effect by
using a LimitTokenCountAnalyzer
.
All .indexwriter
parameters are Lucene specific
and Hibernate Search is just passing these parameters through - see Section 3.7.1, “Tuning indexing performance” for more details.
The MassIndexer
uses a forward only
scrollable result to iterate on the primary keys to be loaded, but MySQL's
JDBC driver will load all values in memory; to avoid this "optimisation"
set idFetchSize
to
Integer.MIN_VALUE
.
This section explains some low level tricks to keep your indexes at peak performance. We cover some Lucene details which in most cases you don't have to know about: Hibernate Search will handle these operations optimally and transparently in most cases without the need for further configuration. Still, it is good to know that there are ways to configure the behaviour, if the need arises.
The index is physically stored in several smaller segments. Each segment is immutable and represents a generation of index writes. Index segments are periodically compacted, both to merge smaller segments and to remove stale entries; this merging process happens constantly in the background and can be tuned with the options specified in Section 3.7.1, “Tuning indexing performance”, but you can also define policies to fully run index optimizations when it is most suited for your specific workload.
With older versions of Lucene it was important to frequently optimize the index to maintain good performance, but with current Lucene versions this doesn't apply anymore. The benefit of explicit optimization is very low, and in certain cases even counter-productive. During an explicit optimization the whole index is processed and rewritten inflicting a significant performance cost. Optimization is for this reason a double-edged sword.
Another reason to avoid optimizing the index too often is that an optimization will, as a side effect, invalidate cached filters and field caches and internal buffers need to be refreshed.
Optimizing the index is often not needed, does not benefit write (update) performance at all, and is a slow operation: make sure you need it before activating it.
Of course optimizing the index does not only present drawbacks: after
the optimization process is completed and new
IndexReader
instances have loaded their buffers,
queries will perform at peak performance and you will have reclaimed all
disk space potentially used by stale entries.
It is recommended to not schedule any optimization, but if you wish to perform it periodically you should run it:
on an idle system or when the searches are less frequent
after a lot of index modifications
When using a MassIndexer
(see Section 6.3.2, “Using a MassIndexer”) it will optimize involved indexes
by default at the start and at the end of processing; you can change this
behavior by using
MassIndexer
.optimizeAfterPurge
and
MassIndexer
.optimizeOnFinish
respectively. The initial optimization is actually very cheap as it is
performed on an emtpy index: its purpose is to release the storage space
occupied by the old index.
While in most cases this is not needed, Hibernate Search can automatically optimize an index after:
a certain amount of write operations
or after a certain amount of transactions
The configuration for automatic index optimization can be defined on a global level or per index:
Example 7.1. Defining automatic optimization parameters
hibernate.search.default.optimizer.operation_limit.max = 1000 hibernate.search.default.optimizer.transaction_limit.max = 100 hibernate.search.Animal.optimizer.transaction_limit.max = 50
With the above example an optimization will be triggered to the
Animal
index as soon as either:
the number of additions and deletions reaches 1000
the number of transactions reaches 50
(hibernate.search.Animal.optimizer.transaction_limit.max
having priority over
hibernate.search.default.optimizer.transaction_limit.max
)
If none of these parameters are defined, no optimization is processed automatically.
The default implementation of OptimizerStrategy can be overriden by
implementing
org.hibernate.search.store.optimization.OptimizerStrategy
and setting the optimizer.implementation
property to
the fully qualified name of your implementation. This implementation must
implement the interface, be a public class and have a public constructor
taking no arguments.
Example 7.2. Loading a custom OptimizerStrategy
hibernate.search.default.optimizer.implementation = com.acme.worlddomination.SmartOptimizer hibernate.search.default.optimizer.SomeOption = CustomConfigurationValue hibernate.search.humans.optimizer.implementation = default
The keyword default
can be used to select the
Hibernate Search default implementation; all properties after the
.optimizer
key separator will be passed to the
implementation's initialize
method at
start.
You can programmatically optimize (defragment) a Lucene index from
Hibernate Search through the SearchFactory
:
Example 7.3. Programmatic index optimization
FullTextSession fullTextSession = Search.getFullTextSession(regularSession);
SearchFactory searchFactory = fullTextSession.getSearchFactory();
searchFactory.optimize(Order.class);
// or
searchFactory.optimize();
The first example optimizes the Lucene index holding
Order
s; the second, optimizes all indexes.
searchFactory.optimize()
has no effect on a JMS
or JGroups backend: you must apply the optimize operation on the Master
node.
The Lucene index is constantly being merged in the background to keep a good balance between write and read performance; in a sense this is a form of background optimization which is always applied.
The following match attributes of Lucene's IndexWriter
and are commonly used to tune how often merging occurs and how aggressive it is
applied. They are exposed by Hibernate Search via:
hibernate.search.[default|<indexname>].indexwriter.max_buffered_docs
hibernate.search.[default|<indexname>].indexwriter.max_merge_docs
hibernate.search.[default|<indexname>].indexwriter.merge_factor
hibernate.search.[default|<indexname>].indexwriter.ram_buffer_size
hibernate.search.[default|<indexname>].indexwriter.term_index_interval
See Section 3.7.1, “Tuning indexing performance” for a description of these properties.
Hibernate Search offers access to a Statistics
object via SearchFactory.getStatistics()
. It allows
you for example to determine which classes are indexed and how many entities
are in the index. This information is always available. However, by
specifying the hibernate.search.generate_statistics
property in your configuration you can also collect total and average Lucene
query and object loading timings.
You can also enable access to the statistics via JMX. Setting the
property hibernate.search.jmx_enabled
will
automatically register the StatisticsInfoMBean
.
Depending on your the configuration the
IndexControlMBean
and
IndexingProgressMonitorMBean
will also be
registered. In case you are having more than one JMX enabled Hibernate
Search instance running within a single JVM, you should also set
hibernate.search.jmx_bean_suffix to a different value
for each of the instances. The specified suffix will be used to
distinguish between the different MBean instances. Let's have a closer
look at the mentioned MBeans.
If you want to access your JMX beans remotely via JConsole make
sure to set the system property
com.sun.management.jmxremote
to
true
.
This MBean gives you access to Statistics
object as desribed in the previous section.
This MBean allows to build, optimize and purge the index for a
given entity. Indexing occurs via the mass indexing API (seeSection 6.3.2, “Using a MassIndexer”). A requirement for this bean
to be registered in JMX is, that the Hibernate
SessionFactory
is bound to JNDI via the
hibernate.session_factory_name
property. Refer to the
Hibernate Core manual for more information on how to configure JNDI. The
IndexControlMBean
and its API are for now
experimental.
This MBean is an implementation
MassIndexerProgressMonitor
interface. If
hibernate.search.jmx_enabled
is enabled and the mass
indexer API is used the indexing progress can be followed via this bean.
The bean will only be bound to JMX while indexing is in progress. Once
indexing is completed the MBean is not longer available.
With the Spatial extensions you can combine fulltext queries with restrictions based on distance from a point in space, filter results based on distances from coordinates or sort results on such a distance criteria.
The spatial support of Hibernate Search has a few goals:
Enable spatial search on entities: find entities within x km from a location (latitude, longitude) on Earth
Provide an easy way to enable spatial indexing via expressive annotations
Provide a simple way for querying
Hide geographical complexity
For example, you might search for that Italian place named approximately "Il Ciociaro" and is somewhere in the 2 km area around your office.
To be able to filter an @Indexed
@Entity
on a distance criteria you need to add the @Spatial
annotation (org.hibernate.search.annotations.Spatial
)
and specify one or more sets of coordinates.
There are different techniques to index point coordinates, in particular Hibernate Search Spatial offers a choice between two strategies:
as numbers formatted for range queries
in Quad-Tree labels for two stage spatial queries
We will now describe both methods so you can make a suitable choice; of
course you can pick different strategies for each set of coordinates.
These strategies are selected by specifying spatialMode
,
an attribute of the @Spatial
annotation.
When setting the @Spatial
.spatialMode
attribute to SpatialMode
.RANGE
(which is the default) coordinates are indexed as numeric fields,
so that range queries can be performed to narrow down the initial area
of interest.
Pros:
Is quick on small data sets (< 100k entities)
Is very simple: straightforward to debug/analyze
Impact on index size is moderate
Cons:
Poor performance on large data sets
Poor performance if your data set is distributed across the whole world (for example when indexing points of interest in the United States, in Europe and in Asia, large areas collide because they share the same latitude. The latitude range query returns large amounts of data that need to be cross checked with those returned by the longitude range).
To index your entities for range querying you have to:
add the @Spatial
annotation on your entity
add the @Latitude
and
@Longitude
annotations on your properties representing
the coordinates; these must be of type Double
Example 9.1. Sample Spatial indexing: Hotel class
import org.hibernate.search.annotations.*;
@Spatial @Indexed @Entity
public class Hotel {
@Latitude
Double latitude
@Longitude
Double longitude
[..]
When setting @Spatial
.spatialMode
to SpatialMode
.GRID
the coordinates are encoded in several fields representing different
zoom levels. Each box for each level is labelled so coordinates are assigned
matching labels for each zoom level. This results in a tree encoding of
labels called quad tree
.
Pros :
Good performance even with large data sets
World wide data distribution independent
Cons :
Index size is larger: need to encode multiple labels per pair of coordinates
To index your entities you have to:
add the @Spatial
annotation on the
entity with the SpatialMode
set to GRID :
@Spatial(spatialMode = SpatialMode.GRID)
add the @Latitude
and
@Longitude
annotations on the properties
representing your coordinates; these must be of type
Double
Example 9.2. Indexing coordinates in a Grid using Quad Trees
@Spatial(spatialMode = SpatialMode.GRID)
@Indexed
@Entity
public class Hotel {
@Latitude
Double latitude;
@Longitude
Double longitude;
[...]
Instead of using the @
Latitude
and @
Longitue
annotations
you can choose to implement the org.hibernate.search.spatial.Coordinates
interface.
Example 9.3. Implementing the Coordinates interface
import org.hibernate.search.annotations.*;
import org.hibernate.search.spatial.Coordinates;
@Spatial @Indexed @Entity
public class Song implements Coordinates {
@Id long id;
double latitude;
double longitude;
[...]
@Override
Double getLatitude() {
return latitude;
}
@Override
Double getLongitude() {
return longitude;
}
[...]
As we will see in the section Section 9.3, “Multiple Coordinate pairs”,
a @
Spatial
@
Indexed
@
Entity
can have multiple @
Spatial
annotations;
when having the entity implement Coordinates
, the implemented
methods refer to the default Spatial name: the default pair of coordinates.
An alternative is to use properties implementing the Coordinates
interface; this way you can have multiple Spatial instances:
Example 9.4. Using attributes of type Coordinates
@Indexed @Entity
public class Event {
@Id
Integer id;
@Field(store = Store.YES)
String name;
double latitude;
double longitude;
@Spatial(spatialMode = SpatialMode.GRID)
public Coordinates getLocation() {
return new Coordinates() {
@Override
public Double getLatitude() {
return latitude;
}
@Override
public Double getLongitude() {
return longitude;
}
};
}
[...]
When using this form the @
Spatial
.name
automatically defaults to the propery name.
The Hibernate Search DSL has been extended to support the spatial
feature. You can build a query to search around a pair of coordinates
(latitude,longitude) or around a bean implementing the Coordinates
interface.
As with any fulltext queries, also for Spatial queries you:
retrieve a QueryBuilder
from the
SearchFactory
as a starting point
use the DSL to build a spatial query with your search center and radius
optionally combine the resulting Query with other filters
call the createFullTextQuery()
and use
run it as any standard Hibernate or JPA Query
Example 9.5. Search for an Hotel by distance
QueryBuilder builder = fullTextSession.getSearchFactory()
.buildQueryBuilder().forEntity( Hotel.class ).get();
org.apache.lucene.search.Query luceneQuery = builder.spatial()
.onDefaultCoordinates()
.within( radius, Unit.KM )
.ofLatitude( centerLatitude )
.andLongitude( centerLongitude )
.createQuery();
org.hibernate.Query hibQuery = fullTextSession.createFullTextQuery( luceneQuery,
Hotel.class );
List results = hibQuery.list();
A fully working example can be found in the source code, in the
testsuite. See
SpatialIndexingTest.testSpatialAnnotationOnClassLevel()
and in the Hotel
class.
As an alternative to passing separate values for latitude and longitude
values, you can also pass an object implementing the Coordinates
interface:
Example 9.6. DSL example with Coordinates
Coordinates coordinates = Point.fromDegrees(24d, 31.5d);
Query query = builder
.spatial()
.onCoordinates( "location" )
.within( 51, Unit.KM )
.ofCoordinates( coordinates )
.createQuery();
List results = fullTextSession.createFullTextQuery( query, POI.class ).list();
To get the distance to the center of the search returned with the results you just need to project it:
Example 9.7. Distance projection example
double centerLatitude = 24.0d;
double centerLongitude= 32.0d;
QueryBuilder builder = fullTextSession.getSearchFactory()
.buildQueryBuilder().forEntity(POI.class).get();
org.apache.lucene.search.Query luceneQuery = builder.spatial()
.onCoordinates("location")
.within(100, Unit.KM)
.ofLatitude(centerLatitude)
.andLongitude(centerLongitude)
.createQuery();
FullTextQuery hibQuery = fullTextSession.createFullTextQuery(luceneQuery, POI.class);
hibQuery.setProjection(FullTextQuery.SPATIAL_DISTANCE, FullTextQuery.THIS);
hibQuery.setSpatialParameters(centerLatitude, centerLongitude, "location");
List results = hibQuery.list();
Use
FullTextQuery
.setProjection
with FullTextQuery.SPATIAL_DISTANCE as one of the projected
fields.
Call
FullTextQuery
.setSpatialParameters
with the latitude, longitude and the name of the spatial field used
to build the spatial query. Note that using coordinates different thans
the center used for the query will have unexpected results.
Using distance projection on non @Spatial enabled entities and/or with a non spatial Query will have unexpected results as entities not spatially indexed and/or having null values for latitude or longitude will be considered to be at (0,0)/(lat,0)/(0,long).
Using distance projection with a spatial query on spatially
indexed entities having, eventually, null
values for
latitude and/or longitude is safe as they will not be found by the
spatial query and won't have distance calculated.
To sort the results by distance to the center of the search you
will have to build a Sort object using a
DistanceSortField
:
Example 9.8. Distance sort example
double centerLatitude = 24.0d;
double centerLongitude = 32.0d;
QueryBuilder builder = fullTextSession.getSearchFactory()
.buildQueryBuilder().forEntity( POI.class ).get();
org.apache.lucene.search.Query luceneQuery = builder.spatial()
.onCoordinates("location")
.within(100, Unit.KM)
.ofLatitude(centerLatitude)
.andLongitude(centerLongitude)
.createQuery();
FullTextQuery hibQuery = fullTextSession.createFullTextQuery(luceneQuery, POI.class);
Sort distanceSort = new Sort(
new DistanceSortField(centerLatitude, centerLongitude, "location"));
hibQuery.setSort(distanceSort);
The DistanceSortField
must be constructed
using the same coordinates on the same spatial field used to build the
spatial query otherwise the sorting will occur with another center than
the query. This repetition is needed to allow you to define Queries with
any tool.
Using distance sort on non @Spatial enabled entities and/or with a non spatial Query will have also unexpected results as entities non spatially indexed and/or with null values for latitude or longitude will be considered to be at (0,0)/(lat,0)/(0,long)
Using distance sort with a spatial query on spatially indexed
entities having, potentially, null
values for latitude
and/or longitude is safe as they will not be found by the spatial query
and so won't be sorted
You can associate multiple pairs of coordinates to the same entity,
as long as each pair is uniquelly identified by using a different name. This is achieved
by stacking multiple @
Spatial
annotations in a @
Spatials
annotation,
and specifying the name
attribute on the
@
Spatial
annotation.
Example 9.9. Multiple sets of coordinates
import org.hibernate.search.annotations.*;
@Spatials({
@Spatial,
@Spatial(name="work", spatialMode = SpatialMode.GRID)
})
@Entity
@Indexed
public class UserEx {
@Id
Integer id;
@Latitude
Double homeLatitude;
@Longitude
Double homeLongitude;
@Latitude(of="work")
Double workLatitude;
@Longitude(of="work")
Double workLongitude;
In the example Example 9.5, “Search for an Hotel by distance” we used
onDefaultCoordinates()
which points to the coordinates
defined by a @
Spatial
annotation
whose name
attribute was not specified.
To target an alternative pair of coordinates at query time, we need
to specify the pair by name using onCoordinates
(String)
instead of
onDefaultCoordinates()
:
Example 9.10. Querying on non-default coordinate set
QueryBuilder builder = fullTextSession.getSearchFactory()
.buildQueryBuilder().forEntity( UserEx.class ).get();
org.apache.lucene.search.Query luceneQuery = builder.spatial()
.onCoordinates( "work" )
.within( radius, Unit.KM )
.ofLatitude( centerLatitude )
.andLongitude( centerLongitude )
.createQuery();
org.hibernate.Query hibQuery = fullTextSession.createFullTextQuery( luceneQuery,
Hotel.class );
List results = hibQuery.list();
The present chapter is meant to provide a technical insight in quad-tree (grid) indexing: how coordinates are mapped to the index and how queries are implemented.
When Hibernate Search indexes the entity annotated with @Spatial, it instantiates a SpatialFieldBridge to transform the latitude and longitude fields accessed via the Coordinates interface to the multiple index fields stored in the Lucene index.
Principle of the spatial index: the spatial index used in Hibernate Search is a QuadTree (http://en.wikipedia.org/wiki/Quadtree).
To make computation in a flat coordinates system the latitude and longitude field values will be projected with a sinusoidal projection ( http://en.wikipedia.org/wiki/Sinusoidal_projection). Origin values space is :
[-90 -> +90],]-180 -> 180]
for latitude,longitude coordinates and projected space is:
]-pi -> +pi],[-pi/2 -> +pi/2]
for cartesian x,y coordinates (beware of fields order inversion: x is longitude and y is latitude).
The index is divided into n levels labeled from 0 to n-1.
At the level 0 the projected space is the whole Earth. At the level 1 the projected space is devided into 4 rectangles (called boxes as in bounding box):
[-pi,-pi/2]->[0,0], [-pi,0]->[0,+pi/2], [0,-pi/2]->[+pi,0] and [0,0]->[+pi,+pi/2]
At level n+1 each box of level n is divided into 4 new boxes and so on. The numbers of boxes at a given level is 4^n.
Each box is given an id, in this format: [Box index on the X axis]|[Box index on the Y axis] To calculate the index of a box on an axis we divide the axis range in 2^n slots and find the slot the box belongs to. At the n level the indexes on an axis are from -(2^n)/2 to (2^n)/2. For instance, the 5th level has 4^5 = 1024 boxes with 32 indexes on each axis (32x32 is 1024) and the box of Id "0|8" is covering the [0,8/32*pi/2]->[1/32*pi,9/32*pi/2] rectangle is projected space.
Beware! The boxes are rectangles in projected space but the related area on Earth is not a rectangle!
Now that we have all these boxes at all these levels will be indexing points "into" them.
For a point (lat,long) we calculate its projection (x,y) and then we calculate for each level of the spatial index, the ids of the boxes it belongs to.
At each level the point is in one and only one box. For points on the edges the box are considered exclusive n the left side and inclusive on the right i-e ]start,end] (the points are normalized before projection to [-90,+90],]-180,+180]).
We store in the Lucene document corresponding to the entity to index one field for each level of the quad tree. The field is named: [spatial index fields name]_HSSI_[n]. [spatial index fields name] is given either by the parameter at class level annotation or derived from the name of the spatial annoted method of he entitiy, HSSI stands for Hibernate Search Spatial Index and n is the level of the quad tree.
We also store the latitude and longitude as a Numeric field under [spatial index fields name]_HSSI_Latitude and [spatial index fields name]_HSSI_Longitude fields. They will be used to filter precisely results by distance in the second stage of the search.
Now that we have all these fields, what are they used for?
When you ask for a spatial search by providing a search discus (center+radius) we will calculate the boxes ids that do cover the search discus in the projected space, fetch all the documents that belong to these boxes (thus narrowing the number of documents for which we will have to calculate distance to the center) and then filter this subset with a real distance calculation. This is called two level spatial filtering.
For a given search radius there is an optimal quad tree level where the number of boxes to retrieve hall be minimal without bringing back to many documents (level 0 has only 1 box but retrieve all documents). The optimal quad tree level is the maximum level where the width of each box is larger than the search area. Near the equator line where projection deformation is minimal, this will lead to the retrieval of at most 4 boxes. Towards the poles where the deformation is more significant, it might need to examine more boxes but as the sinusoidal projection has a simple Tissot's indicatrix (see http://en.wikipedia.org/wiki/Sinusoidal_projection) in populated areas, the overhead is minimal.
Now that we have chosen the optimal level, we can compute the ids of the boxes covering the search discus (which is not a discus in projected space anymore).
This is done by org.hibernate.search.spatial.impl.SpatialHelper.getQuadTreeCellsIds(Point center, double radius, int quadTreeLevel)
It will calculate the bounding box of the search discus and then
call
org.hibernate.search.spatial.impl.SpatialHelper.getQuadTreeCellsIds(Point
lowerLeft, Point upperRight, int quadTreeLevel) that will do the actual
computation. If the bounding box crosses the meridian line it will cut
the search in two and make two calls to getQuadTreeCellsIds(Point
lowerLeft, Point upperRight, int quadTreeLevel)
with left and
right parts of the box.
There are some geo related hacks (search radius too large, search radius crossing the poles) that are handled in bounding box computations done by Rectangle.fromBoundingCircle(Coordinates center, double radius) (see http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates for reference on those subjects).
The SpatialHelper.getQuadTreeCellsIds(Point lowerLeft, Point upperRight, int quadTreeLevel) project the defining points of the bounding box and compute the boxes they belong to. It returns all the box Ids between the lower left to the upper right corners, thus covering the area.
The Query is build with theses Ids to lookup for documents having a [spatial index fields name]_HSSI_[n] (n the level found at Step 1) field valued with one of the ids of Step 2.
See also the implementation of org.hibernate.search.spatial.impl.QuadTreeFilter
.
This Query will return all documents in the boxes covering the projected bounding box of the search discus. So it is too large and needs refining. But we have narrowed the distance calculation problems to a subet of our datas.
In this final chapter we are offering a smorgasbord of tips and tricks which might become useful as you dive deeper and deeper into Hibernate Search.
The SearchFactory
object keeps track of the
underlying Lucene resources for Hibernate Search. It is a convenient way
to access Lucene natively. The SearchFactory
can be
accessed from a FullTextSession
:
Example 10.1. Accessing the SearchFactory
FullTextSession fullTextSession = Search.getFullTextSession(regularSession);
SearchFactory searchFactory = fullTextSession.getSearchFactory();
Queries in Lucene are executed on an
IndexReader
. Hibernate Search caches index readers
to maximize performance and implements other strategies to retrieve
updated IndexReader
s in order to minimize IO
operations. Your code can access these cached resources, but you have to
follow some "good citizen" rules.
Example 10.2. Accessing an IndexReader
IndexReader reader = searchFactory.getIndexReaderAccessor().open(Order.class);
try {
//perform read-only operations on the reader
}
finally {
searchFactory.getIndexReaderAccessor().close(reader);
}
In this example the SearchFactory
figures out
which indexes are needed to query this entity. Using the configured
ReaderProvider
(described in Reader strategy) on each index, it returns
a compound IndexReader
on top of all involved indexes.
Because this IndexReader
is shared amongst several
clients, you must adhere to the following rules:
Never call indexReader.close(), but always call readerProvider.closeReader(reader), using a finally block.
Don't use this IndexReader
for
modification operations: it's a readonly
IndexReader
, you would get an
exception).
Aside from those rules, you can use the
IndexReader
freely, especially to do native Lucene
queries. Using this shared IndexReader
s will be
more efficient than by opening one directly from - for example - the
filesystem.
As an alternative to the method open(Class...
types)
you can use open(String...
indexNames)
; in this case you pass in one or more index
names; using this strategy you can also select a subset of the indexes for
any indexed type if sharding is used.
Example 10.3. Accessing an IndexReader by index
names
IndexReader reader = searchFactory
.getIndexReaderAccessor()
.open("Products.1", "Products.3");
A Directory
is the most common abstraction
used by Lucene to represent the index storage; Hibernate Search doesn't
interact directly with a Lucene Directory
but
abstracts these interactions via an IndexManager
:
an index does not necessarily need to be implemented by a
Directory
.
If you are certain that your index is represented as a
Directory
and need to access it, you can get a
reference to the Directory
via the
IndexManager
. You will have to cast the
IndexManager
instance to a
DirectoryBasedIndexManager
and then use
getDirectoryProvider().getDirectory()
to get a
reference to the underlying Directory
. This is not
recommended, if you need low level access to the index using Lucene APIs
we suggest to see Section 10.2, “Using an IndexReader” instead.
In some cases it can be useful to split (shard) the data into several Lucene indexes. There are two main use use cases:
A single index is so big that index update times are slowing the application down. In this case static sharding can be used to split the data into a pre-defined number of shards.
Data is naturally segmented by customer, region, language or other application parameter and the index should be split according to these segments. This is a use case for dynamic sharding.
By default sharding is not enabled.
To enable static sharding set the
hibernate.search.<indexName>.sharding_strategy.nbr_of_shards
property as seen in Example 10.4, “Enabling index sharding”.
Example 10.4. Enabling index sharding
hibernate.search.[default|<indexName>].sharding_strategy.nbr_of_shards = 5
The default sharding strategy which gets enabled by setting this
property, splits the data according to the hash value of the document id
(generated by the FieldBridge
). This ensures a
fairly balanced sharding. You can replace the default strategy by
implementing a custom IndexShardingStrategy
. To
use your custom strategy you have to set the
hibernate.search.[default|<indexName>].sharding_strategy
property to the fully qualified class name of your custom
IndexShardingStrategy
.
Example 10.5. Registering a custom IndexShardingStrategy
hibernate.search.[default|<indexName>].sharding_strategy = my.custom.RandomShardingStrategy
Dynamic sharding allows you to manage the shards yourself and even
create new shards on the fly. To do so you need to implement the
interface ShardIdentifierProvider
and set the
hibernate.search.[default|<indexName>].sharding_strategy
property to the fully qualified name of this class. Note that instead of
implementing the interface directly, you should rather derive your
implementation from
org.hibernate.search.store.ShardIdentifierProviderTemplate
which provides a basic implementation. Let's look at Example 10.6, “Custom ShardidentiferProvider
” for an
example.
Example 10.6. Custom ShardidentiferProvider
public static class AnimalShardIdentifierProvider extends ShardIdentifierProviderTemplate { @Override public String getShardIdentifier(Class<?> entityType, Serializable id, String idAsString, Document document) { if ( entityType.equals(Animal.class) ) { String type = document.getFieldable("type").stringValue(); addShard(type); return type; } throw new RuntimeException("Animal expected but found " + entityType); } @Override protected Set<String> loadInitialShardNames(Properties properties, BuildContext buildContext) { ServiceManager serviceManager = buildContext.getServiceManager(); SessionFactory sessionFactory = serviceManager.requestService( HibernateSessionFactoryServiceProvider.class, buildContext); Session session = sessionFactory.openSession(); try { Criteria initialShardsCriteria = session.createCriteria(Animal.class); initialShardsCriteria.setProjection( Projections.distinct(Property.forName("type"))); @SuppressWarnings("unchecked") List<String> initialTypes = initialShardsCriteria.list(); return new HashSet<String>(initialTypes); } finally { session.close(); } } }
The are several things happening in
AnimalShardIdentifierProvider
. First off its
purpose is to create one shard per animal type (e.g. mammal, insect,
etc.). It does so by inspecting the class type and the Lucene document
passed to the getShardIdentifier()
method. It
extracts the type
field from the document and uses
it as shard name. getShardIdentifier()
is
called for every addition to the index and a new shard will be created
with every new animal type encountered. The base class
ShardIdentifierProviderTemplate
maintains a set
with all known shards to which any identifier must be added by calling
addShard()
.
It is important to understand that Hibernate Search cannot know which
shards already exist when the application starts. When using
ShardIdentifierProviderTemplate
as base class of
a ShardIdentifierProvider
implementation, the
initial set of shard identifiers must be returned by the
loadInitialShardNames()
method. How this is
done will depend on the use case. However, a common case in combination
with Hibernate ORM is that the initial shard set is defined by the the
distinct values of a given database column. Example 10.6, “Custom ShardidentiferProvider
” shows how to handle
such a case. AnimalShardIdentifierProvider
makes
in its loadInitialShardNames()
implementation
use of a service called
HibernateSessionFactoryServiceProvider
(see also
Section 10.6, “Using external services”) which is available within an ORM
environment. It allows to request a Hibernate
SessionFactory
instance which can be used to run
a Criteria
query in order to determine the
initial set of shard identifers.
Last but not least, the
ShardIdentifierProvider
also allows for
optimizing searches by selecting which shard to run a query against. By
activating a filter (see Section 5.3.1, “Using filters in a sharded environment”), a
sharding strategy can select a subset of the shards used to answer a
query (getShardIdentifiersForQuery()
, not shown
in the example) and thus speed up the query execution.
This ShardIdentifierProvider
is considered
experimental. We might need to apply some changes to the defined method
signatures to accomodate for unforeseen use cases. Please provide
feedback if you have ideas, or just to let us know how you're using
this API.
It is technically possible to store the information of more than one entity into a single Lucene index. There are two ways to accomplish this:
Configuring the underlying directory providers to point to the
same physical index directory. In practice, you set the property
hibernate.search.[fully qualified entity
name].indexName
to the same value. As an example let’s use
the same index (directory) for the Furniture
and Animal
entity. We just set
indexName
for both entities to for example
“Animal”. Both entities will then be stored in the Animal
directory.
hibernate.search.org.hibernate.search.test.shards.Furniture.indexName = Animal hibernate.search.org.hibernate.search.test.shards.Animal.indexName = Animal
Setting the @Indexed
annotation’s
index
attribute of the entities you want to
merge to the same value. If we again wanted all
Furniture
instances to be indexed in the
Animal
index along with all instances of
Animal
we would specify
@Indexed(index="Animal")
on both
Animal
and Furniture
classes.
This is only presented here so that you know the option is available. There is really not much benefit in sharing indexes.
Any of the pluggable contracts we have seen so far allows for the
injection of a service. The most notable example being the
DirectoryProvider
. The full list is:
DirectoryProvider
ReaderProvider
OptimizerStrategy
BackendQueueProcessor
Worker
ErrorHandler
MassIndexerProgressMonitor
Some of these components need to access a service which is either
available in the environment or whose lifecycle is bound to the
SearchFactory
. Sometimes, you even want the same
service to be shared amongst several instances of these contract. One
example is the ability the share an Infinispan cache instance between
several directory providers running in different JVM
s
to store the various indexes using the same underlying infrastructure;
this provides real-time replication of indexes across nodes.
To expose a service, you need to implement
org.hibernate.search.spi.ServiceProvider<T>
.
T
is the type of the service you want to use.
Services are retrieved by components via their
ServiceProvider
class implementation.
If your service ought to be started when Hibernate Search starts
and stopped when Hibernate Search stops, you can use a managed
service. Make sure to properly implement the
start
and stop
methods of ServiceProvider
. When the service is
requested, the getService
method is
called.
Example 10.7. Example of ServiceProvider implementation
public class CacheServiceProvider implements ServiceProvider<Cache> {
private CacheManager manager;
public void start(Properties properties) {
//read configuration
manager = new CacheManager(properties);
}
public Cache getService() {
return manager.getCache(DEFAULT);
}
void stop() {
manager.close();
}
}
The ServiceProvider
implementation must
have a no-arg constructor.
To be transparently discoverable, such service should have an
accompanying
META-INF/services/org.hibernate.search.spi.ServiceProvider
whose content list the (various) service provider
implementation(s).
Example 10.8. Content of META-INF/services/org.hibernate.search.spi.ServiceProvider
com.acme.infra.hibernate.CacheServiceProvider
Alternatively, the service can be provided by the environment
bootstrapping Hibernate Search. For example, Infinispan which uses
Hibernate Search as its internal search engine can pass the
CacheContainer
to Hibernate Search. In this
case, the CacheContainer
instance is not
managed by Hibernate Search and the
start
/stop
methods
of its corresponding service provider will not be used.
Provided services have priority over managed services. If a
provider service is registered with the same
ServiceProvider
class as a managed service,
the provided service will be used.
The provided services are passed to Hibernate Search via the
SearchConfiguration
interface
(getProvidedServices
).
Provided services are used by frameworks controlling the lifecycle of Hibernate Search and not by traditional users.
If, as a user, you want to retrieve a service instance from the environment, use registry services like JNDI and look the service up in the provider.
Many of of the pluggable contracts of Hibernate Search can use
services. Services are accessible via the
BuildContext
interface.
Example 10.9. Example of a directory provider using a cache service
public CustomDirectoryProvider implements DirectoryProvider<RAMDirectory> {
private BuildContext context;
public void initialize(
String directoryProviderName,
Properties properties,
BuildContext context) {
//initialize
this.context = context;
}
public void start() {
Cache cache = context.requestService(CacheServiceProvider.class);
//use cache
}
public RAMDirectory getDirectory() {
// use cache
}
public stop() {
//stop services
context.releaseService(CacheServiceProvider.class);
}
}
When you request a service, an instance of the service is served
to you. Make sure to then release the service. This is fundamental. Note
that the service can be released in the
DirectoryProvider.stop
method if the
DirectoryProvider
uses the service during its
lifetime or could be released right away of the service is simply used
at initialization time.
Lucene allows the user to customize its scoring formula by extending
org.apache.lucene.search.Similarity
. The abstract
methods defined in this class match the factors of the following formula
calculating the score of query q for document d:
score(q,d) = coord(q,d) · queryNorm(q) · ∑ t in q ( tf(t in d) · idf(t) 2 · t.getBoost() · norm(t,d) )
Factor | Description |
---|---|
tf(t ind) | Term frequency factor for the term (t) in the document (d). |
idf(t) | Inverse document frequency of the term. |
coord(q,d) | Score factor based on how many of the query terms are found in the specified document. |
queryNorm(q) | Normalizing factor used to make scores between queries comparable. |
t.getBoost() | Field boost. |
norm(t,d) | Encapsulates a few (indexing time) boost and length factors. |
It is beyond the scope of this manual to explain this
formula in more detail. Please refer to
Similarity
's Javadocs for more information.
Hibernate Search provides two ways to modify Lucene's similarity calculation.
First you can set the default similarity by specifying the fully
specified classname of your Similarity
implementation using the property
hibernate.search.similarity
. The default value is
org.apache.lucene.search.DefaultSimilarity
.
Secondly, you can override the similarity used for a specific index
by setting the similarity
property for this index (see
Section 3.3, “Directory configuration” for more information
about index configuration):
hibernate.search.[default|<indexname>].similarity = my.custom.Similarity
As an example, let's assume it is not important how often a term
appears in a document. Documents with a single occurrence of the term
should be scored the same as documents with multiple occurrences. In this
case your custom implementation of the method tf(float freq)
should return 1.0.
When two entities share the same index they must declare the same
Similarity
implementation.
The use of @Similarity
which was used to
configure the similarity on a class level is deprecated since Hibernate
Search 4.4. Instead of using the annotation use the configuration
property.
Last but not least, a few pointers to further information. We highly recommend you to get a copy Hibernate Search in Action. This excellent book covers Hibernate Search in much more depth than this online documentation can and has a great range of additional examples. If you want to increase your knowledge of Lucene we recommend Lucene in Action (Second Edition). Because Hibernate Search's functionality is tightly coupled to Hibernate Core it is a good idea to understand Hibernate. Start with the online documentation or get hold of a copy of Java Persistence with Hibernate.
If you have any further questions regarding Hibernate Search or want to share some of your use cases have a look at the Hibernate Search Wiki and the Hibernate Search Forum. We are looking forward hearing from you.
In case you would like to report a bug use the Hibernate Search JIRA instance. Feedback is always welcome!