DbSettings (JBoss Application Server: Build 7.1.2.Final API)

java.lang.Object
- org.h2.engine.SettingsBase
- - org.h2.constant.DbSettings

```
public class DbSettings
extends SettingsBase
```
This class contains various database-level settings. To override the documented default value for a database, append the setting in the database URL: "jdbc:h2:test;ALIAS_COLUMN_NAME=TRUE" when opening the first connection to the database. The settings can not be changed once the database is open.
Some settings are a last resort and temporary solution to work around a problem in the application or database engine. Also, there are system properties to enable features that are not yet fully tested or that are not backward compatible.

Field Summary

Fields
Modifier and Type	Field and Description
`boolean`	`aliasColumnName` Database setting `ALIAS_COLUMN_NAME` (default: false). When enabled, aliased columns (as in SELECT ID AS I FROM TEST) return the alias (I in this case) in ResultSetMetaData.getColumnName() and 'null' in getTableName().
`int`	`analyzeAuto` Database setting `ANALYZE_AUTO` (default: 2000). After changing this many rows, ANALYZE is automatically run for a table.
`int`	`analyzeSample` Database setting `ANALYZE_SAMPLE` (default: 10000). The default sample size when analyzing a table.
`boolean`	`databaseToUpper` Database setting `DATABASE_TO_UPPER` (default: true). Database short names are converted to uppercase for the DATABASE() function, and in the CATALOG column of all database meta data methods.
`boolean`	`dbCloseOnExit` Database setting `DB_CLOSE_ON_EXIT` (default: true). Close the database when the virtual machine exits normally, using a shutdown hook.
`boolean`	`defaultConnection` Database setting `DEFAULT_CONNECTION` (default: false). Whether Java functions can use `DriverManager.getConnection("jdbc:default:connection")` to get a database connection.
`String`	`defaultEscape` Database setting `DEFAULT_ESCAPE` (default: \). The default escape character for LIKE comparisons.
`boolean`	`defragAlways` Database setting `DEFRAG_ALWAYS` (default: false). Each time the database is closed, it is fully defragmented (SHUTDOWN DEFRAG).
`boolean`	`dropRestrict` Database setting `DROP_RESTRICT` (default: true). Whether the default action for DROP TABLE and DROP VIEW is RESTRICT.
`boolean`	`earlyFilter` Database setting `EARLY_FILTER` (default: false). This setting allows table implementations to apply filter conditions early on.
`int`	`estimatedFunctionTableRows` Database setting `ESTIMATED_FUNCTION_TABLE_ROWS` (default: 1000). The estimated number of rows in a function table (for example, CSVREAD or FTL_SEARCH).
`boolean`	`functionsInSchema` Database setting `FUNCTIONS_IN_SCHEMA` (default: true). If set, all functions are stored in a schema.
`int`	`largeResultBufferSize` Database setting `LARGE_RESULT_BUFFER_SIZE` (default: 4096). Buffer size for large result sets.
`boolean`	`largeTransactions` Database setting `LARGE_TRANSACTIONS` (default: true). Support very large transactions
`int`	`maxCompactCount` Database setting `MAX_COMPACT_COUNT` (default: Integer.MAX_VALUE). The maximum number of pages to move when closing a database.
`int`	`maxCompactTime` Database setting `MAX_COMPACT_TIME` (default: 200). The maximum time in milliseconds used to compact a database when closing.
`int`	`maxMemoryRowsDistinct` Database setting `MAX_MEMORY_ROWS_DISTINCT` (default: 10000). The maximum number of rows kept in-memory for SELECT DISTINCT queries.
`int`	`maxQueryTimeout` Database setting `MAX_QUERY_TIMEOUT` (default: 0). The maximum timeout of a query in milliseconds.
`boolean`	`nestedJoins` Database setting `NESTED_JOINS` (default: true). Whether nested joins should be supported.
`boolean`	`optimizeDistinct` Database setting `OPTIMIZE_DISTINCT` (default: true). Improve the performance of simple DISTINCT queries if an index is available for the given column.
`boolean`	`optimizeEvaluatableSubqueries` Database setting `OPTIMIZE_EVALUATABLE_SUBQUERIES` (default: true). Optimize subqueries that are not dependent on the outer query.
`boolean`	`optimizeInList` Database setting `OPTIMIZE_IN_LIST` (default: true). Optimize IN(...) and IN(SELECT ...) comparisons.
`boolean`	`optimizeInSelect` Database setting `OPTIMIZE_IN_SELECT` (default: true). Optimize IN(SELECT ...) comparisons.
`boolean`	`optimizeInsertFromSelect` Database setting `OPTIMIZE_INSERT_FROM_SELECT` (default: true). Insert into table from query directly bypassing temporary disk storage.
`boolean`	`optimizeIsNull` Database setting `OPTIMIZE_IS_NULL` (default: false). Use an index for condition of the form columnName IS NULL.
`boolean`	`optimizeOr` Database setting `OPTIMIZE_OR` (default: true). Convert (C=? OR C=?) to (C IN(?, ?)).
`boolean`	`optimizeTwoEquals` Database setting `OPTIMIZE_TWO_EQUALS` (default: true). Optimize expressions of the form A=B AND B=1.
`boolean`	`optimizeUpdate` Database setting `OPTIMIZE_UPDATE` (default: true). Speed up inserts, updates, and deletes by not reading all rows from a page unless necessary.
`boolean`	`pageStoreInternalCount` Database setting `PAGE_STORE_INTERNAL_COUNT` (default: false). Update the row counts on a node level.
`int`	`pageStoreMaxGrowth` Database setting `PAGE_STORE_MAX_GROWTH` (default: 128 * 1024). The maximum number of pages the file grows at any time.
`boolean`	`pageStoreTrim` Database setting `PAGE_STORE_TRIM` (default: true). Trim the database size when closing.
`int`	`queryCacheSize` Database setting `QUERY_CACHE_SIZE` (default: 8). The size of the query cache.
`boolean`	`recompileAlways` Database setting `RECOMPILE_ALWAYS` (default: false). Always recompile prepared statements.
`int`	`reconnectCheckDelay` Database setting `RECONNECT_CHECK_DELAY` (default: 200). Check the .lock.db file every this many milliseconds to detect that the database was changed.
`boolean`	`rowId` Database setting `ROWID` (default: true). If set, each table has a pseudo-column _ROWID_.
`boolean`	`selectForUpdateMvcc` Database setting `SELECT_FOR_UPDATE_MVCC` (default: true). If set, SELECT ..
`boolean`	`shareLinkedConnections` Database setting `SHARE_LINKED_CONNECTIONS` (default: true). Linked connections should be shared, that means connections to the same database should be used for all linked tables that connect to the same database.

Method Summary

Methods
Modifier and Type Method and Description

static DbSettings getInstance(HashMap<String,String> s)
INTERNAL.
- Methods inherited from class org.h2.engine.SettingsBase
  containsKey, get, get, get, getSettings
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods
Modifier and Type	Method and Description
`static DbSettings`	`getInstance(HashMap<String,String> s)` INTERNAL.

- Field Detail
  - aliasColumnName
```
public final boolean aliasColumnName
```
    Database setting ALIAS_COLUMN_NAME (default: false).
    When enabled, aliased columns (as in SELECT ID AS I FROM TEST) return the alias (I in this case) in ResultSetMetaData.getColumnName() and 'null' in getTableName(). If disabled, the real column name (ID in this case) and table name is returned.
    This setting only affects the default and the MySQL mode. When using any other mode, this feature is enabled for compatibility, even if this database setting is not enabled explicitly.
  - analyzeAuto
```
public final int analyzeAuto
```
    Database setting ANALYZE_AUTO (default: 2000).
    After changing this many rows, ANALYZE is automatically run for a table. Automatically running ANALYZE is disabled if set to 0. If set to 1000, then ANALYZE will run against each user table after about 1000 changes to that table. The time between running ANALYZE doubles each time since starting the database. It is not run on local temporary tables, and tables that have a trigger on SELECT.
  - analyzeSample
```
public final int analyzeSample
```
    Database setting ANALYZE_SAMPLE (default: 10000).
    The default sample size when analyzing a table.
  - databaseToUpper
```
public final boolean databaseToUpper
```
    Database setting DATABASE_TO_UPPER (default: true).
    Database short names are converted to uppercase for the DATABASE() function, and in the CATALOG column of all database meta data methods. Setting this to "false" is experimental. When set to false, all identifier names (table names, column names) are case sensitive (except aggregate, built-in functions, data types, and keywords).
  - dbCloseOnExit
```
public final boolean dbCloseOnExit
```
    Database setting DB_CLOSE_ON_EXIT (default: true).
    Close the database when the virtual machine exits normally, using a shutdown hook.
  - defaultConnection
```
public boolean defaultConnection
```
    Database setting DEFAULT_CONNECTION (default: false).
    Whether Java functions can use DriverManager.getConnection("jdbc:default:connection") to get a database connection. This feature is disabled by default for performance reasons. Please note the Oracle JDBC driver will try to resolve this database URL if it is loaded before the H2 driver.
  - defaultEscape
```
public final String defaultEscape
```
    Database setting DEFAULT_ESCAPE (default: \).
    The default escape character for LIKE comparisons. To select no escape character, use an empty string.
  - defragAlways
```
public final boolean defragAlways
```
    Database setting DEFRAG_ALWAYS (default: false).
    Each time the database is closed, it is fully defragmented (SHUTDOWN DEFRAG).
  - dropRestrict
```
public final boolean dropRestrict
```
    Database setting DROP_RESTRICT (default: true).
    Whether the default action for DROP TABLE and DROP VIEW is RESTRICT.
  - earlyFilter
```
public final boolean earlyFilter
```
    Database setting EARLY_FILTER (default: false).
    This setting allows table implementations to apply filter conditions early on.
  - estimatedFunctionTableRows
```
public final int estimatedFunctionTableRows
```
    Database setting ESTIMATED_FUNCTION_TABLE_ROWS (default: 1000).
    The estimated number of rows in a function table (for example, CSVREAD or FTL_SEARCH). This value is used by the optimizer.
  - functionsInSchema
```
public final boolean functionsInSchema
```
    Database setting FUNCTIONS_IN_SCHEMA (default: true).
    If set, all functions are stored in a schema. Specially, the SCRIPT statement will always include the schema name in the CREATE ALIAS statement. This is not backward compatible with H2 versions 1.2.134 and older.
  - largeResultBufferSize
```
public final int largeResultBufferSize
```
    Database setting LARGE_RESULT_BUFFER_SIZE (default: 4096).
    Buffer size for large result sets. Set this value to 0 to disable the buffer.
  - largeTransactions
```
public final boolean largeTransactions
```
    Database setting LARGE_TRANSACTIONS (default: true).
    Support very large transactions
  - maxCompactCount
```
public final int maxCompactCount
```
    Database setting MAX_COMPACT_COUNT (default: Integer.MAX_VALUE).
    The maximum number of pages to move when closing a database.
  - maxCompactTime
```
public final int maxCompactTime
```
    Database setting MAX_COMPACT_TIME (default: 200).
    The maximum time in milliseconds used to compact a database when closing.
  - maxMemoryRowsDistinct
```
public final int maxMemoryRowsDistinct
```
    Database setting MAX_MEMORY_ROWS_DISTINCT (default: 10000).
    The maximum number of rows kept in-memory for SELECT DISTINCT queries. If more than this number of rows are in a result set, a temporary table is used.
  - maxQueryTimeout
```
public int maxQueryTimeout
```
    Database setting MAX_QUERY_TIMEOUT (default: 0).
    The maximum timeout of a query in milliseconds. The default is 0, meaning no limit. Please note the actual query timeout may be set to a lower value.
  - nestedJoins
```
public final boolean nestedJoins
```
    Database setting NESTED_JOINS (default: true).
    Whether nested joins should be supported.
  - optimizeDistinct
```
public final boolean optimizeDistinct
```
    Database setting OPTIMIZE_DISTINCT (default: true).
    Improve the performance of simple DISTINCT queries if an index is available for the given column. The optimization is used if:
    - The select is a single column query without condition
    - The query contains only one table, and no group by
    - There is only one table involved
    - There is an ascending index on the column
    - The selectivity of the column is below 20
  - optimizeEvaluatableSubqueries
```
public final boolean optimizeEvaluatableSubqueries
```
    Database setting OPTIMIZE_EVALUATABLE_SUBQUERIES (default: true).
    Optimize subqueries that are not dependent on the outer query.
  - optimizeInsertFromSelect
```
public final boolean optimizeInsertFromSelect
```
    Database setting OPTIMIZE_INSERT_FROM_SELECT (default: true).
    Insert into table from query directly bypassing temporary disk storage. This also applies to create table as select.
  - optimizeInList
```
public final boolean optimizeInList
```
    Database setting OPTIMIZE_IN_LIST (default: true).
    Optimize IN(...) and IN(SELECT ...) comparisons. This includes optimization for SELECT, DELETE, and UPDATE.
  - optimizeInSelect
```
public final boolean optimizeInSelect
```
    Database setting OPTIMIZE_IN_SELECT (default: true).
    Optimize IN(SELECT ...) comparisons. This includes optimization for SELECT, DELETE, and UPDATE.
  - optimizeIsNull
```
public final boolean optimizeIsNull
```
    Database setting OPTIMIZE_IS_NULL (default: false).
    Use an index for condition of the form columnName IS NULL.
  - optimizeOr
```
public final boolean optimizeOr
```
    Database setting OPTIMIZE_OR (default: true).
    Convert (C=? OR C=?) to (C IN(?, ?)).
  - optimizeTwoEquals
```
public final boolean optimizeTwoEquals
```
    Database setting OPTIMIZE_TWO_EQUALS (default: true).
    Optimize expressions of the form A=B AND B=1. In this case, AND A=1 is added so an index on A can be used.
  - optimizeUpdate
```
public final boolean optimizeUpdate
```
    Database setting OPTIMIZE_UPDATE (default: true).
    Speed up inserts, updates, and deletes by not reading all rows from a page unless necessary.
  - pageStoreMaxGrowth
```
public final int pageStoreMaxGrowth
```
    Database setting PAGE_STORE_MAX_GROWTH (default: 128 * 1024).
    The maximum number of pages the file grows at any time.
  - pageStoreInternalCount
```
public final boolean pageStoreInternalCount
```
    Database setting PAGE_STORE_INTERNAL_COUNT (default: false).
    Update the row counts on a node level.
  - pageStoreTrim
```
public final boolean pageStoreTrim
```
    Database setting PAGE_STORE_TRIM (default: true).
    Trim the database size when closing.
  - queryCacheSize
```
public final int queryCacheSize
```
    Database setting QUERY_CACHE_SIZE (default: 8).
    The size of the query cache. Each session has it's own cache with the given size. The cache is only used if the SQL statement and all parameters match. Only the last returned result per query is cached. Only SELECT statements are cached (excluding UNION and FOR UPDATE statements). This works for both statements and prepared statement.
  - recompileAlways
```
public final boolean recompileAlways
```
    Database setting RECOMPILE_ALWAYS (default: false).
    Always recompile prepared statements.
  - reconnectCheckDelay
```
public final int reconnectCheckDelay
```
    Database setting RECONNECT_CHECK_DELAY (default: 200).
    Check the .lock.db file every this many milliseconds to detect that the database was changed. The process writing to the database must first notify a change in the .lock.db file, then wait twice this many milliseconds before updating the database.
  - rowId
```
public final boolean rowId
```
    Database setting ROWID (default: true).
    If set, each table has a pseudo-column _ROWID_.
  - selectForUpdateMvcc
```
public final boolean selectForUpdateMvcc
```
    Database setting SELECT_FOR_UPDATE_MVCC (default: true).
    If set, SELECT .. FOR UPDATE queries lock only the selected rows when using MVCC.
  - shareLinkedConnections
```
public final boolean shareLinkedConnections
```
    Database setting SHARE_LINKED_CONNECTIONS (default: true).
    Linked connections should be shared, that means connections to the same database should be used for all linked tables that connect to the same database.
- Method Detail
  - getInstance
```
public static DbSettings getInstance(HashMap<String,String> s)
```
    INTERNAL. Get the settings for the given properties (may be null).
    
    Parameters:
    s - the settings
    
    Returns:
    the settings

Class DbSettings

Field Summary

Method Summary

Methods inherited from class org.h2.engine.SettingsBase

Methods inherited from class java.lang.Object

Field Detail

aliasColumnName

analyzeAuto

analyzeSample

databaseToUpper

dbCloseOnExit

defaultConnection

defaultEscape

defragAlways

dropRestrict

earlyFilter

estimatedFunctionTableRows

functionsInSchema

largeResultBufferSize

largeTransactions

maxCompactCount

maxCompactTime

maxMemoryRowsDistinct

maxQueryTimeout

nestedJoins

optimizeDistinct

optimizeEvaluatableSubqueries

optimizeInsertFromSelect

optimizeInList

optimizeInSelect

optimizeIsNull

optimizeOr

optimizeTwoEquals

optimizeUpdate

pageStoreMaxGrowth

pageStoreInternalCount

pageStoreTrim

queryCacheSize

recompileAlways

reconnectCheckDelay

rowId

selectForUpdateMvcc

shareLinkedConnections

Method Detail

getInstance