org.h2.engine

Class DbSettings

java.lang.Object

org.h2.engine.SettingsBase

org.h2.engine.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	compressData Database setting COMPRESS (default: false). Compress data when storing.
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.
java.lang.String	defaultEscape Database setting DEFAULT_ESCAPE (default: \). The default escape character for LIKE comparisons.
java.lang.String	defaultTableEngine Database setting DEFAULT_TABLE_ENGINE (default: null). The default table engine to use for new tables.
boolean	defragAlways Database setting DEFRAG_ALWAYS (default: false). Each time the database is closed normally, it is fully defragmented (the same as 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.
boolean	largeTransactions Database setting LARGE_TRANSACTIONS (default: true). Support very large transactions
int	lobTimeout Database setting LOB_TIMEOUT (default: 300000, which means 5 minutes). The number of milliseconds a temporary LOB reference is kept until it times out.
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	maxQueryTimeout Database setting MAX_QUERY_TIMEOUT (default: 0). The maximum timeout of a query in milliseconds.
boolean	multiThreaded Database setting MULTI_THREADED (default: false).
boolean	mvStore Database setting MV_STORE (default: false for version 1.3, true for version 1.4). Use the MVStore storage engine.
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, in number of cached statements.
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	reuseSpace Database setting REUSE_SPACE (default: true). If disabled, all changes are appended to the database file, and existing content is never overwritten.
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	getDefaultSettings() INTERNAL.
static DbSettings	getInstance(java.util.HashMap<java.lang.String,java.lang.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

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 java.lang.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 normally, it is fully defragmented (the same as SHUTDOWN DEFRAG). If you execute SHUTDOWN COMPACT, then this setting is ignored.

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.

largeTransactions

public final boolean largeTransactions

Database setting LARGE_TRANSACTIONS (default: true).
Support very large transactions

lobTimeout

public final int lobTimeout

Database setting LOB_TIMEOUT (default: 300000, which means 5 minutes).
The number of milliseconds a temporary LOB reference is kept until it times out. After the timeout, the LOB is no longer accessible using this reference.

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.

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, in number of cached statements. 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. The following statement types are cached: SELECT statements are cached (excluding UNION and FOR UPDATE statements), CALL if it returns a single value, DELETE, INSERT, MERGE, UPDATE, and transactional statements such as COMMIT. 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.

reuseSpace

public final boolean reuseSpace

Database setting REUSE_SPACE (default: true).
If disabled, all changes are appended to the database file, and existing content is never overwritten. This setting has no effect if the database is already open.

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.

defaultTableEngine

public final java.lang.String defaultTableEngine

Database setting DEFAULT_TABLE_ENGINE (default: null).
The default table engine to use for new tables.

mvStore

public boolean mvStore

Database setting MV_STORE (default: false for version 1.3, true for version 1.4).
Use the MVStore storage engine.

compressData

public final boolean compressData

Database setting COMPRESS (default: false).
Compress data when storing.

multiThreaded

public final boolean multiThreaded

Database setting MULTI_THREADED (default: false).

Method Detail

getInstance

public static DbSettings getInstance(java.util.HashMap<java.lang.String,java.lang.String> s)

INTERNAL. Get the settings for the given properties (may not be null).

Parameters:

s - the settings

Returns:

the settings

getDefaultSettings

public static DbSettings getDefaultSettings()

INTERNAL. Get the default settings. Those must not be modified.

Returns:

the settings