DbSettingsThis 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;ANALYZE_SAMPLE=1000" 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. analyzeAutoDatabase 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.analyzeSampleDatabase setting
ANALYZE_SAMPLE (default: 10000).
The default sample size when analyzing a table.autoCompactFillRateDatabase setting
AUTO_COMPACT_FILL_RATE
(default: 90, which means 90%, 0 disables auto-compacting).
Set the auto-compact target fill rate. If the average fill rate (the
percentage of the storage space that contains active data) of the
chunks is lower, then the chunks with a low fill rate are re-written.
Also, if the percentage of empty space between chunks is higher than
this value, then chunks at the end of the file are moved. Compaction
stops if the target fill rate is reached.
This setting only affects MVStore engine.caseInsensitiveIdentifiersDatabase setting
CASE_INSENSITIVE_IDENTIFIERS (default:
false).
When set to true, all identifier names (table names, column names) are
case insensitive. Setting this to "true" is experimental.compressDataDatabase setting
COMPRESS
(default: false).
Compress data when storing.databaseToLowerDatabase setting
DATABASE_TO_LOWER (default: false).
When set to true unquoted identifiers and short name of database are
converted to lower case. Value of this setting should not be changed
after creation of database. Setting this to "true" is experimental.databaseToUpperDatabase setting
DATABASE_TO_UPPER (default: true).
When set to true unquoted identifiers and short name of database are
converted to upper case.dbCloseOnExitDatabase setting
DB_CLOSE_ON_EXIT (default: true).
Close the database when the virtual machine exits normally, using a
shutdown hook.defaultConnectionDatabase 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.defaultEscapeDatabase setting
DEFAULT_ESCAPE (default: \).
The default escape character for LIKE comparisons. To select no escape
character, use an empty string.defaultTableEngineDatabase setting
DEFAULT_TABLE_ENGINE
(default: null).
The default table engine to use for new tables.defragAlwaysDatabase 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.dropRestrictDatabase setting
DROP_RESTRICT (default: true)
Whether the default action for DROP TABLE, DROP VIEW, DROP SCHEMA, DROP
DOMAIN, and DROP CONSTRAINT is RESTRICT.estimatedFunctionTableRowsDatabase 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.ignoreCatalogsDatabase setting
IGNORE_CATALOGS
(default: false).
If set, all catalog names in identifiers are silently accepted
without comparing them with the short name of the database.lobTimeoutDatabase 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.maxCompactTimeDatabase setting
MAX_COMPACT_TIME (default: 200).
The maximum time in milliseconds used to compact a database when closing.maxQueryTimeoutDatabase 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.mvStoreDatabase setting
MV_STORE
(default: true).
Use the MVStore storage engine.optimizeDistinctDatabase 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:
optimizeEvaluatableSubqueriesDatabase setting
OPTIMIZE_EVALUATABLE_SUBQUERIES (default:
true).
Optimize subqueries that are not dependent on the outer query.optimizeInListDatabase setting
OPTIMIZE_IN_LIST (default: true).
Optimize IN(...) and IN(SELECT ...) comparisons. This includes
optimization for SELECT, DELETE, and UPDATE.optimizeInSelectDatabase setting
OPTIMIZE_IN_SELECT (default: true).
Optimize IN(SELECT ...) comparisons. This includes
optimization for SELECT, DELETE, and UPDATE.optimizeInsertFromSelectDatabase 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.optimizeOrDatabase setting
OPTIMIZE_OR (default: true).
Convert (C=? OR C=?) to (C IN(?, ?)).optimizeSimpleSingleRowSubqueriesDatabase setting
OPTIMIZE_SIMPLE_SINGLE_ROW_SUBQUERIES (default: true).
Optimize expressions of the form (SELECT A) to A.optimizeTwoEqualsDatabase 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.queryCacheSizeDatabase 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.recompileAlwaysDatabase setting
RECOMPILE_ALWAYS (default: false).
Always recompile prepared statements.reuseSpaceDatabase 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.shareLinkedConnectionsDatabase 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.zeroBasedEnumsDatabase setting
ZERO_BASED_ENUMS
(default: false).
If set, ENUM ordinal values are 0-based. |