DbSettings

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.




Fields
static boolean aliasColumnName
static int analyzeAuto
static int analyzeSample
static boolean databaseToUpper
static boolean dbCloseOnExit
static boolean defaultConnection
static String defaultEscape
static String defaultTableEngine
static boolean defragAlways
static boolean dropRestrict
static boolean earlyFilter
static int estimatedFunctionTableRows
static boolean functionsInSchema
static int largeResultBufferSize
static boolean largeTransactions
static int maxCompactCount
static int maxCompactTime
static int maxMemoryRowsDistinct
static int maxQueryTimeout
static boolean mvStore
static boolean nestedJoins
static boolean optimizeDistinct
static boolean optimizeEvaluatableSubqueries
static boolean optimizeInList
static boolean optimizeInSelect
static boolean optimizeInsertFromSelect
static boolean optimizeIsNull
static boolean optimizeOr
static boolean optimizeTwoEquals
static boolean optimizeUpdate
static boolean pageStoreInternalCount
static int pageStoreMaxGrowth
static boolean pageStoreTrim
static int queryCacheSize
static boolean recompileAlways
static int reconnectCheckDelay
static boolean rowId
static boolean selectForUpdateMvcc
static boolean shareLinkedConnections

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

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

Database setting ANALYZE_SAMPLE (default: 10000).
The default sample size when analyzing a table.

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

Database setting DB_CLOSE_ON_EXIT (default: true).
Close the database when the virtual machine exits normally, using a shutdown hook.

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

Database setting DEFAULT_ESCAPE (default: \).
The default escape character for LIKE comparisons. To select no escape character, use an empty string.

defaultTableEngine

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

defragAlways

Database setting DEFRAG_ALWAYS (default: false).
Each time the database is closed, it is fully defragmented (SHUTDOWN DEFRAG).

dropRestrict

Database setting DROP_RESTRICT (default: true).
Whether the default action for DROP TABLE and DROP VIEW is RESTRICT.

earlyFilter

Database setting EARLY_FILTER (default: false).
This setting allows table implementations to apply filter conditions early on.

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

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

Database setting LARGE_RESULT_BUFFER_SIZE (default: 4096).
Buffer size for large result sets. Set this value to 0 to disable the buffer.

largeTransactions

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

maxCompactCount

Database setting MAX_COMPACT_COUNT (default: Integer.MAX_VALUE).
The maximum number of pages to move when closing a database.

maxCompactTime

Database setting MAX_COMPACT_TIME (default: 200).
The maximum time in milliseconds used to compact a database when closing.

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

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.

mvStore

Database setting MV_STORE (default: false).
Use the MVStore storage engine.

nestedJoins

Database setting NESTED_JOINS (default: true).
Whether nested joins should be supported.

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

Database setting OPTIMIZE_EVALUATABLE_SUBQUERIES (default: true).
Optimize subqueries that are not dependent on the outer query.

optimizeInList

Database setting OPTIMIZE_IN_LIST (default: true).
Optimize IN(...) and IN(SELECT ...) comparisons. This includes optimization for SELECT, DELETE, and UPDATE.

optimizeInSelect

Database setting OPTIMIZE_IN_SELECT (default: true).
Optimize IN(SELECT ...) comparisons. This includes optimization for SELECT, DELETE, and UPDATE.

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.

optimizeIsNull

Database setting OPTIMIZE_IS_NULL (default: false).
Use an index for condition of the form columnName IS NULL.

optimizeOr

Database setting OPTIMIZE_OR (default: true).
Convert (C=? OR C=?) to (C IN(?, ?)).

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

Database setting OPTIMIZE_UPDATE (default: true).
Speed up inserts, updates, and deletes by not reading all rows from a page unless necessary.

pageStoreInternalCount

Database setting PAGE_STORE_INTERNAL_COUNT (default: false).
Update the row counts on a node level.

pageStoreMaxGrowth

Database setting PAGE_STORE_MAX_GROWTH (default: 128 * 1024).
The maximum number of pages the file grows at any time.

pageStoreTrim

Database setting PAGE_STORE_TRIM (default: true).
Trim the database size when closing.

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

Database setting RECOMPILE_ALWAYS (default: false).
Always recompile prepared statements.

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

Database setting ROWID (default: true).
If set, each table has a pseudo-column _ROWID_.

selectForUpdateMvcc

Database setting SELECT_FOR_UPDATE_MVCC (default: true).
If set, SELECT .. FOR UPDATE queries lock only the selected rows when using MVCC.

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.