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;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.




Fields
static int analyzeAuto
static int analyzeSample
static int autoCompactFillRate
static boolean caseInsensitiveIdentifiers
static boolean compressData
static boolean databaseToLower
static boolean databaseToUpper
static boolean dbCloseOnExit
static boolean defaultConnection
static String defaultEscape
static String defaultTableEngine
static boolean defragAlways
static boolean dropRestrict
static int estimatedFunctionTableRows
static boolean ignoreCatalogs
static int lobTimeout
static int maxCompactTime
static int maxQueryTimeout
static boolean mvStore
static boolean optimizeDistinct
static boolean optimizeEvaluatableSubqueries
static boolean optimizeInList
static boolean optimizeInSelect
static boolean optimizeInsertFromSelect
static boolean optimizeOr
static boolean optimizeSimpleSingleRowSubqueries
static boolean optimizeTwoEquals
static int queryCacheSize
static boolean recompileAlways
static boolean reuseSpace
static boolean shareLinkedConnections
static boolean zeroBasedEnums

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.

autoCompactFillRate

Database 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.

caseInsensitiveIdentifiers

Database 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.

compressData

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

databaseToLower

Database 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.

databaseToUpper

Database setting DATABASE_TO_UPPER (default: true). When set to true unquoted identifiers and short name of database are converted to upper case.

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

dropRestrict

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

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.

ignoreCatalogs

Database 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.

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.

maxCompactTime

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

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: true). Use the MVStore storage engine.

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.

optimizeOr

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

optimizeSimpleSingleRowSubqueries

Database setting OPTIMIZE_SIMPLE_SINGLE_ROW_SUBQUERIES (default: true). Optimize expressions of the form (SELECT A) to A.

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.

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.

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.

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.

zeroBasedEnums

Database setting ZERO_BASED_ENUMS (default: false). If set, ENUM ordinal values are 0-based.