org.h2.constant
Class DbSettings

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

boolean	aliasColumnName Database setting ALIAS_COLUMN_NAME (default: false).
int	analyzeAuto Database setting ANALYZE_AUTO (default: 0).
int	analyzeSample Database setting ANALYZE_SAMPLE (default: 10000).
boolean	databaseToUpper Database setting DATABASE_TO_UPPER (default: true).
boolean	dbCloseOnExit Database setting DB_CLOSE_ON_EXIT (default: true).
java.lang.String	defaultEscape Database setting DEFAULT_ESCAPE (default: \).
boolean	defragAlways Database setting DEFRAG_ALWAYS (default: false).
boolean	dropRestrict Database setting DROP_RESTRICT (default: false).
int	estimatedFunctionTableRows Database setting ESTIMATED_FUNCTION_TABLE_ROWS (default: 1000).
boolean	functionsInSchema Database setting FUNCTIONS_IN_SCHEMA (default: false).
int	largeResultBufferSize Database setting LARGE_RESULT_BUFFER_SIZE (default: 4096).
boolean	largeTransactions Database setting LARGE_TRANSACTIONS (default: false).
int	maxCompactCount Database setting MAX_COMPACT_COUNT (default: Integer.MAX_VALUE).
int	maxCompactTime Database setting MAX_COMPACT_TIME (default: 200).
int	maxMemoryRowsDistinct Database setting MAX_MEMORY_ROWS_DISTINCT (default: Integer.MAX_VALUE).
int	maxQueryTimeout Database setting MAX_QUERY_TIMEOUT (default: 0).
boolean	nestedJoins Database setting NESTED_JOINS (default: false).
boolean	optimizeDistinct Database setting OPTIMIZE_DISTINCT (default: true).
boolean	optimizeEvaluatableSubqueries Database setting OPTIMIZE_EVALUATABLE_SUBQUERIES (default: true).
boolean	optimizeInList Database setting OPTIMIZE_IN_LIST (default: true).
boolean	optimizeInsertFromSelect Database setting OPTIMIZE_INSERT_FROM_SELECT (default: false).
boolean	optimizeIsNull Database setting OPTIMIZE_IS_NULL (default: false).
boolean	optimizeOr Database setting OPTIMIZE_OR (default: false).
boolean	optimizeSubqueryCache Database setting OPTIMIZE_SUBQUERY_CACHE (default: true).
boolean	optimizeTwoEquals Database setting OPTIMIZE_TWO_EQUALS (default: true).
boolean	optimizeUpdate Database setting OPTIMIZE_UPDATE (default: true).
boolean	pageStoreInternalCount Database setting PAGE_STORE_INTERNAL_COUNT (default: false).
boolean	pageStoreTrim Database setting PAGE_STORE_TRIM (default: true).
int	queryCacheSize Database setting QUERY_CACHE_SIZE (default: 0).
boolean	recompileAlways Database setting RECOMPILE_ALWAYS (default: false).
int	reconnectCheckDelay Database setting RECONNECT_CHECK_DELAY (default: 200).
boolean	selectForUpdateMvcc Database setting SELECT_FOR_UPDATE_MVCC (default: false).
boolean	shareLinkedConnections Database setting SHARE_LINKED_CONNECTIONS (default: true).

Method Summary

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: 0).
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.

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.

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, it is fully defragmented (SHUTDOWN DEFRAG).

dropRestrict

public final boolean dropRestrict

Database setting DROP_RESTRICT (default: false).
Whether the default action for DROP TABLE and DROP VIEW is RESTRICT. For most databases, the default action is RESTRICT, but for compatibility with older versions of H2 the default action is currently CASCADE. This will change in a future version of H2.

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: false).
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: false).
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: Integer.MAX_VALUE).
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: false).
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: false).
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.

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: false).
Convert (C=? OR C=?) to (C IN(?, ?)).

optimizeSubqueryCache

public final boolean optimizeSubqueryCache

Database setting OPTIMIZE_SUBQUERY_CACHE (default: true).
Cache subquery results.

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.

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: 0).
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.

selectForUpdateMvcc

public final boolean selectForUpdateMvcc

Database setting SELECT_FOR_UPDATE_MVCC (default: false).
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(java.util.HashMap<java.lang.String,java.lang.String> s)

INTERNAL. Get the settings for the given properties (may be null).

Parameters:

s - the settings

Returns:

the settings