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A VDB or virtual database definition is contained in an XML file. For .vdb archive files created in the design tool, this file is embedded in the archive and most field can be updated through tooling. The XML schema for this file can be found in the teiid-docs/schema directory.
Example 12.1. Example VDB XML
<vdb name="${vdb-name}" version="${vdb-version}">
<!-- VDB properties -->
<property name="UseConnectorMetadata" value="..." />
...
<!-- define a model fragment for each data source -->
<model name="${model-name}">
<property name="..." value="..." />
...
<source name="${source-name}" translator-name="${translator-name}"
connection-jndi-name="${deployed-jndi-name}">
...
</model>
<!-- create translator instances that override default properties -->
<translator name="${translator-name}" type="${translator-type}" />
<property name="..." value="..." />
...
</translator>
</vdb>
Attributes
name
The name of the VDB. The VDB name referenced through the driver or datasource during the connection time.
version
The version of the VDB (should be an positive integer). This determines the deployed directory location (see Name), and provides an explicit versioning mechanism to the VDB name.
Property Elements
UseConnectorMetadata
Setting to use connector
supplied metadata. Can be "true" or "cached". "true" will obtain
metadata once for every launch of Teiid. "cached" will save a file
containing the metadata into the
PROFILE/data/teiid
query-timeout
Sets the default query timeout in milliseconds for queries executed against this VDB. 0 indicates that the server default query timeout should be used. Defaults to 0. Will have no effect if the server default query timeout is set to a lesser value. Note that clients can still set their own timeouts that will be managed on the client side.
Attributes
name
The name of the model is used as a top level schema name for all of the metadata imported from the connector. The name should be unique among all Models in the VDB and should not contain the '.' character.
version
The version of the VDB (should be an positive integer). This determines the deployed directory location (see Name), and provides an explicit versioning mechanism to the VDB name.
Source Element
A source is a named binding of a translator and connection source to a model.
name
The name of the source to use for this model. This can be any name you like, but will typically be the same as the model name. Having a name different than the model name is only useful in multi-source scenarios. In multi-source, the source names under a given model must be unique. If you have the same source bound to multiple models it may have the same name for each. An exception will be raised if the same source name is used for different sources.
translator-name
The name or type of the Teiid Translator to use. Possible values include the built-in types (ws, file, ldap, oracle, sqlserver, db2, derby, etc.) and translators defined in the translators section.
connection-jndi-name
The JNDI name of this source's connection factory. There should be a corresponding "-ds.xml" file that defines the connection factory in the JBoss AS. Check out the deploying VDB dependencies section for info. You also need to deploy these connection factories before you can deploy the VDB.
Property Elements
importer.<propertyname>
Property to be used by the connector importer for the model for purposes importing metadata. See possible property name/values in the Translator specific section. Note that using these properties you can narrow or widen the data elements available for integration.
Attributes
name
The name of the the Translator. Referenced by the source element.
type
The base type of the Translator. Can be one of the built-in types (ws, file, ldap, oracle, sqlserver, db2, derby, etc.).
Property Elements
Set a value that overrides a translator default property. See possible property name/values in the Translator specific section.
Teiid integration is available via a "Dynamic VDB" without the need for Teiid Designer tooling. While this mode of operation does not yet allow for the creation of view layers, the underlying sources can still be queried as if they are a single source. See the kit's "teiid-example/dynamicvdb-*" for working examples.
To build a dynamic VDB, you'll need to create a
SOME-NAME-vdb.xml
VDB name pattern must adhere to "-vdb.xml" for the Teiid VDB deployer to recognize this file as a dynamic VDB.
my-vdb.xml: (The vdb-deployer.xml schema for this file is available in the schema folder under the docs with the Teiid distribution.)
Multi-source models can be used to quickly access data in multiple sources with homogeneous metadata. When you have multiple instances of data that are using identical schema (horizontal sharding), Teiid can help you aggregate data across all the instances, using "multi-source" models. In this scenario, instead of creating/importing a model for every data source, user needs to define one source model that represents the schema and configure multiple data "sources" underneath it. During runtime, when a query issued against this model, the query engine analyzes the information and gathers the required data from all the sources configured and aggregates the results and provides in a single result set. Since all sources utilize the same physical metadata, this feature is most appropriate for accessing the same source type with multiple instances.
To mark a model as multi-source, the user needs to supply property called supports-multi-source-bindings, in the "vdb.xml" file. Also, the user needs to define multiple sources. Here is code example showing dynamic vdb with single model with multiple sources defined.
<vdb name="vdbname" version="1">
<model visible="true" type="PHYSICAL" name="Customers" path="/Test/Customers.xmi">
<property name="supports-multi-source-bindings" value="true"/>
<source name="chicago"
translator-name="oracle" connection-jndi-name="chicago-customers"/>
<source name="newyork"
translator-name="oracle" connection-jndi-name="newyork-customers"/>
<source name="la"
translator-name="oracle" connection-jndi-name="la-customers"/>
</model>
</vdb>
In the above example, the VDB defined has single model called Customers,
that has multiple sources (chicago, newyork,
and la) that define different instances of data. Every
time a model is marked as "multi-source", the
runtime engine adds a additional column called "SOURCE_NAME" to every table in
that model. This column maps to the source's name from the XML. In
the above XML code that would be chicago, la,
newyork. This allows queries like the following:
select * from table where SOURCE_NAME = 'newyork'
update table column=value where SOURCE_NAME='chicago'
delete from table where column = x and SOURCE_NAME='la'
insert into table (column, SOURCE_NAME) VALUES ('value', 'newyork')Note that when user do not supply the "SOURCE_NAME" in the criteria, the command applies to all the sources. If SOURCE_NAME supplied, the query is executed only aginst the source specified. Another useful feature along with this feature is "partial results" to skip unavailable sources if they are down.
More complex partitioning scenarios, such as heterogeneous sources or list partitioning will require the use of a Section 14.2.8, “Partitioned Union”.
Currently the tooling support for managing the multi-source feature is limited, so if you need to use this feature build the VDB as usual in the Teiid Designer and then edit the "vdb.xml" file in the VDB archive using a Text editor to add the additional sources as defined above. You must deploy a separate data source for each source defined in the xml file.
If you would like to use "SOURCE_NAME" in your transformations to control which sources are accessed or updated, you would manually need to add this extra column on your view table in the Designer. This column will not be automatically added on the source table, when you import the medata from source. It is important to understand that a column or IN procedure parameter named source_name in multi-source mode will always be treated as the explicit form of the multi-source source_name column and will no longer be treated as an actual physical column or procedure parameter.
A multi-source SELECT may use the source_name column anywhere a column reference is allowed. As a final stage of planning, a source query will be generated against each source and each instance of the source_name column replaced by the appropriate value. If the resulting query still needs executed, it is sent to the source. If the WHERE clause evaluates to always false, then the query is pruned from the result. All results are then unioned together and returned as the full result.
A multi-source INSERT may use the source_name column as an insert target column to specify which source should be targeted by the INSERT. Only a INSERT using the VALUES clause is supported and the source_name column value must be a literal. If the source_name column is not part of the INSERT column, then the INSERT will be issued against every source. The sum of the update counts will be returned as the resultant update count.
A multi-source delete functions just like SELECT, however it is not possible to use the source_name column as a target column in the change set. Any other usage of the source_name column will be the appropriate value for each source. If the WHERE clause evaluates to always false, then no update will be issued to the source. The sum of the update counts will be returned as the resultant update count.
A multi-source delete functions just like SELECT. Any usage of the source_name column will be the appropriate value for each source. If the WHERE clause evaluates to always false, then no delete will be issued to the source. The sum of the update counts will be returned as the resultant update count.
A physical stored procedures requires the manual addition of a string source_name parameter to allow for specifying which source the procedure is executed on. If the source_name parameter is not added or if named parameters are used and the source_name parameter is allowed to default to a null value, then the procedure will be executed on each source and the results unioned together.
It is not possible to execute procedures that required to return IN/OUT, OUT, or RETURN parameters values on more than 1 source at a time.