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/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.engine;
import java.util.HashMap;
import org.h2.api.ErrorCode;
import org.h2.message.DbException;
/**
* 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.
*
*/
public class DbSettings extends SettingsBase {
/**
* The initial size of the hash table.
*/
static final int TABLE_SIZE = 64;
/**
* INTERNAL.
* The default settings. Those must not be modified.
*/
public static final DbSettings DEFAULT = new DbSettings(new HashMap<>(TABLE_SIZE));
/**
* 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.
*/
public final int analyzeAuto = get("ANALYZE_AUTO", 2000);
/**
* Database setting ANALYZE_SAMPLE (default: 10000).
* The default sample size when analyzing a table.
*/
public final int analyzeSample = get("ANALYZE_SAMPLE", 10_000);
/**
* 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.
*/
public final int autoCompactFillRate = get("AUTO_COMPACT_FILL_RATE", 90);
/**
* 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.
*/
public final boolean databaseToLower;
/**
* Database setting DATABASE_TO_UPPER (default: true).
* When set to true unquoted identifiers and short name of database are
* converted to upper case.
*/
public final boolean databaseToUpper;
/**
* 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.
*/
public final boolean caseInsensitiveIdentifiers = get("CASE_INSENSITIVE_IDENTIFIERS", false);
/**
* 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.
*/
public final boolean defaultConnection = get("DEFAULT_CONNECTION", false);
/**
* Database setting DEFAULT_ESCAPE (default: \).
* The default escape character for LIKE comparisons. To select no escape
* character, use an empty string.
*/
public final String defaultEscape = get("DEFAULT_ESCAPE", "\\");
/**
* 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.
*/
public final boolean defragAlways = get("DEFRAG_ALWAYS", false);
/**
* Database setting DROP_RESTRICT (default: true)
* Whether the default action for DROP TABLE, DROP VIEW, DROP SCHEMA, DROP
* DOMAIN, and DROP CONSTRAINT is RESTRICT.
*/
public final boolean dropRestrict = get("DROP_RESTRICT", true);
/**
* 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.
*/
public final int estimatedFunctionTableRows = get(
"ESTIMATED_FUNCTION_TABLE_ROWS", 1000);
/**
* 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.
*/
public final int lobTimeout = get("LOB_TIMEOUT", 300_000);
/**
* Database setting MAX_COMPACT_TIME (default: 200).
* The maximum time in milliseconds used to compact a database when closing.
*/
public final int maxCompactTime = get("MAX_COMPACT_TIME", 200);
/**
* 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.
*/
public final int maxQueryTimeout = get("MAX_QUERY_TIMEOUT", 0);
/**
* 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
*
*/
public final boolean optimizeDistinct = get("OPTIMIZE_DISTINCT", true);
/**
* Database setting OPTIMIZE_EVALUATABLE_SUBQUERIES (default:
* true).
* Optimize subqueries that are not dependent on the outer query.
*/
public final boolean optimizeEvaluatableSubqueries = get(
"OPTIMIZE_EVALUATABLE_SUBQUERIES", true);
/**
* 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.
*/
public final boolean optimizeInsertFromSelect = get(
"OPTIMIZE_INSERT_FROM_SELECT", true);
/**
* Database setting OPTIMIZE_IN_LIST (default: true).
* Optimize IN(...) and IN(SELECT ...) comparisons. This includes
* optimization for SELECT, DELETE, and UPDATE.
*/
public final boolean optimizeInList = get("OPTIMIZE_IN_LIST", true);
/**
* Database setting OPTIMIZE_IN_SELECT (default: true).
* Optimize IN(SELECT ...) comparisons. This includes
* optimization for SELECT, DELETE, and UPDATE.
*/
public final boolean optimizeInSelect = get("OPTIMIZE_IN_SELECT", true);
/**
* Database setting OPTIMIZE_OR (default: true).
* Convert (C=? OR C=?) to (C IN(?, ?)).
*/
public final boolean optimizeOr = get("OPTIMIZE_OR", true);
/**
* 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.
*/
public final boolean optimizeTwoEquals = get("OPTIMIZE_TWO_EQUALS", true);
/**
* Database setting OPTIMIZE_SIMPLE_SINGLE_ROW_SUBQUERIES (default: true).
* Optimize expressions of the form (SELECT A) to A.
*/
public final boolean optimizeSimpleSingleRowSubqueries = get("OPTIMIZE_SIMPLE_SINGLE_ROW_SUBQUERIES", true);
/**
* 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.
*/
public final int queryCacheSize = get("QUERY_CACHE_SIZE", 8);
/**
* Database setting RECOMPILE_ALWAYS (default: false).
* Always recompile prepared statements.
*/
public final boolean recompileAlways = get("RECOMPILE_ALWAYS", false);
/**
* 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.
*/
public final boolean reuseSpace = get("REUSE_SPACE", true);
/**
* 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.
*/
public final boolean shareLinkedConnections = get(
"SHARE_LINKED_CONNECTIONS", true);
/**
* Database setting DEFAULT_TABLE_ENGINE
* (default: null).
* The default table engine to use for new tables.
*/
public final String defaultTableEngine = get("DEFAULT_TABLE_ENGINE", null);
/**
* Database setting MV_STORE
* (default: true).
* Use the MVStore storage engine.
*/
public final boolean mvStore = get("MV_STORE", true);
/**
* Database setting COMPRESS
* (default: false).
* Compress data when storing.
*/
public final boolean compressData = get("COMPRESS", false);
/**
* 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.
*/
public final boolean ignoreCatalogs = get("IGNORE_CATALOGS", false);
/**
* Database setting ZERO_BASED_ENUMS
* (default: false).
* If set, ENUM ordinal values are 0-based.
*/
public final boolean zeroBasedEnums = get("ZERO_BASED_ENUMS", false);
private DbSettings(HashMap s) {
super(s);
boolean lower = get("DATABASE_TO_LOWER", false);
boolean upperSet = containsKey("DATABASE_TO_UPPER");
boolean upper = get("DATABASE_TO_UPPER", true);
if (lower && upper) {
if (upperSet) {
throw DbException.get(ErrorCode.UNSUPPORTED_SETTING_COMBINATION,
"DATABASE_TO_LOWER & DATABASE_TO_UPPER");
}
upper = false;
}
databaseToLower = lower;
databaseToUpper = upper;
HashMap settings = getSettings();
settings.put("DATABASE_TO_LOWER", Boolean.toString(lower));
settings.put("DATABASE_TO_UPPER", Boolean.toString(upper));
}
/**
* INTERNAL.
* Get the settings for the given properties (may not be null).
*
* @param s the settings
* @return the settings
*/
static DbSettings getInstance(HashMap s) {
return new DbSettings(s);
}
}