Search PostgreSQL documentation

ICU CollationsManual ChaptersPG1823.2.2.3.2. ICU Collations ICU collations can be created like: CREATE COLLATION german (provider = icu, locale = 'de-DE'); ICU locales are specified as a BCP 47 Language Tag, but can also ac…ICU Collations ICU Comparison LevelsManual ChaptersPG1823.2.3.1. ICU Comparison Levels Comparison of two strings (collation) in ICU is determined by a multi-level process, where textual features are grouped into "levels". Treatment of each level…ICU Comparison Levels ICU Custom CollationsManual ChaptersPG1823.2.3. ICU Custom Collations ICU allows extensive control over collation behavior by defining new collations with collation settings as a part of the language tag. These settings can modify…ICU Custom Collations ICU Locale NamesManual ChaptersPG1823.1.5.1. ICU Locale Names The ICU format for the locale name is a Language Tag. CREATE COLLATION mycollation1 (provider = icu, locale = 'ja-JP'); CREATE COLLATION mycollation2 (provider = i…ICU Locale Names ICU LocalesManual ChaptersPG1823.1.5. ICU LocalesICU Locales ICU Tailoring RulesManual ChaptersPG1823.2.3.4. ICU Tailoring Rules If the options provided by the collation settings shown above are not sufficient, the order of collation elements can be changed with tailoring rules, whose syn…ICU Tailoring Rules icu_extExtensionsExtensionsAccess ICU functions icu_ext UtilitiesUtilities · Extensions icu_unicode_versionFunctionsReferenceicu_unicode_version System Information Functions And Operators 17 Returns a string representing the version of Unicode used by ICU, if the server was built with ICU support; otherwise return…Functions · System Information Functions And Operators icu_validation_levelConfigurationReferenceicu_validation_level Client Connection Defaults 16 When ICU locale validation problems are encountered, controls which message level is used to report the problem. Valid values are DISABLED,…Configuration · Client Connection Defaults ideExtensionsExtensionsAquameta IDE events plpgsql postgresql rest-api semantics system-catalog version-control-system widgets ide FeaturesFeatures · Extensions Ident AuthenticationManual ChaptersPG1820.8. Ident Authentication The ident authentication method works by obtaining the client's operating system user name from an ident server and using it as the allowed database user name (wit…Ident Authentication ident_fileConfigurationReferenceident_file File Locations 10 Specifies the configuration file for user name mapping (customarily called pg_ident.conf). This parameter can only be set at server start. See also Section 20.2.…Configuration · File Locations Identifiers and Key WordsManual ChaptersPG184.1.1. Identifiers and Key Words Tokens such as SELECT, UPDATE, or VALUES in the example above are examples of key words, that is, words that have a fixed meaning in the SQL language. The to…Identifiers and Key Words Identifying BugsManual ChaptersPG185.1. Identifying Bugs Before you report a bug, please read and re-read the documentation to verify that you can really do whatever it is you are trying. If it is not clear from the documenta…Identifying Bugs Identity ColumnsManual ChaptersPG185.3. Identity Columns An identity column is a special column that is generated automatically from an implicit sequence. It can be used to generate key values. To create an identity column, u…Identity Columns idle_in_transaction_session_timeoutConfigurationReferenceidle_in_transaction_session_timeout Client Connection Defaults 10 Terminate any session with an open transaction that has been idle for longer than the specified duration in milliseconds. Th…Configuration · Client Connection Defaults idle_replication_slot_timeoutConfigurationReferenceidle_replication_slot_timeout Replication 18 Invalidate replication slots that have remained inactive (not used by a replication connection) for longer than this duration. If this value is s…Configuration · Replication idle_session_timeoutConfigurationReferenceidle_session_timeout Client Connection Defaults 14 Terminate any session that has been idle (that is, waiting for a client query), but not within an open transaction, for longer than the spe…Configuration · Client Connection Defaults idxFunctionsPG18idx ( integer[], item integer ) → integer Returns index of the first array element matching item, or 0 if no match. idx(array[11,22,33,22,11], 22) → 2intarray — manipulate arrays of integers › intarray Functions and Operators IF-THENManual ChaptersPG1841.6.4.1. IF-THEN IF boolean-expression THEN statements END IF; IF-THEN statements are the simplest form of IF. The statements between THEN and END IF will be executed if the condition is tr…IF-THEN IF-THEN-ELSEManual ChaptersPG1841.6.4.2. IF-THEN-ELSE IF boolean-expression THEN statements ELSE statements END IF; IF-THEN-ELSE statements add to IF-THEN by letting you specify an alternative set of statements that shoul…IF-THEN-ELSE IF-THEN-ELSIFManual ChaptersPG1841.6.4.3. IF-THEN-ELSIF IF boolean-expression THEN statements [ ELSIF boolean-expression THEN statements [ ELSIF boolean-expression THEN statements ... ] ] [ ELSE statements ] END IF; Someti…IF-THEN-ELSIF ifdef, ifndef, elif, else, and endif DirectivesManual ChaptersPG1834.9.3. ifdef, ifndef, elif, else, and endif Directives You can use the following directives to compile code sections conditionally: EXEC SQL ifdef name; # Checks a name and processes subseq…ifdef, ifndef, elif, else, and endif Directives ignore-cipher-failureManual ChaptersPG18F.26.3.8.12. ignore-cipher-failure Dangerous! Instructs pgcrypto to use an incorrect decryption algorithm matching the historical behavior prior to the fix for CVE-2026-14663, by completely …ignore-cipher-failure ignore_checksum_failureConfigurationReferenceignore_checksum_failure Developer Options 10 Only has effect if data checksums are enabled. Detection of a checksum failure during a read normally causes PostgreSQL to report an error, abort…Configuration · Developer Options ignore_invalid_pagesConfigurationReferenceignore_invalid_pages Developer Options 13 If set to off (the default), detection of WAL records having references to invalid pages during recovery causes PostgreSQL to raise a PANIC-level er…Configuration · Developer Options ignore_system_indexesConfigurationReferenceignore_system_indexes Developer Options 10 Ignore system indexes when reading system tables (but still update the indexes when modifying the tables). This is useful when recovering from dama…Configuration · Developer Options iifExtensionsExtensionsAdds iif function compatibility compatibility iif iif CompatibilityCompatibility · Extensions imcsExtensionsExtensionsIn-Memory Columnar Store extension for PostgreSQL. analytic columnar store imcs in-memory olap timeseries vertical imcs AnalyticsAnalytics · Extensions imgsmlrExtensionsExtensionsImage similarity with haar imgsmlr FeaturesFeatures · Extensions ImplementationManual ChaptersPG1865.1.4. Implementation This section covers B-Tree index implementation details that may be of use to advanced users. See src/backend/access/nbtree/README in the source distribution for a muc…Implementation ImplementationManual ChaptersPG1865.4.4. Implementation Internally, a GIN index contains a B-tree index constructed over keys, where each key is an element of one or more indexed items (a member of an array, for example) an…Implementation ImplementationManual ChaptersPG1865.2.4. ImplementationImplementation ImplementationManual ChaptersPG1865.6.2. Implementation There are four kinds of pages in a hash index: the meta page (page zero), which contains statically allocated control information; primary bucket pages; overflow pages…Implementation ImplementationManual ChaptersPG1865.3.4. Implementation This section covers implementation details and other tricks that are useful for implementers of SP-GiST operator classes to know.Implementation Implementation DetailsManual ChaptersPG188.7.4. Implementation Details Enum labels are case sensitive, so 'happy' is not the same as 'HAPPY'. White space in the labels is significant too. Although enum types are primarily intended …Implementation Details Implementation FeaturesManual ChaptersPG1833.2. Implementation Features The large object implementation breaks large objects up into “chunks” and stores the chunks in rows in the database. A B-tree index guarantees fast searches for…Implementation Features Implicit Rollback after ExceptionsManual ChaptersPG1841.13.2.1. Implicit Rollback after Exceptions In PL/pgSQL, when an exception is caught by an EXCEPTION clause, all database changes since the block's BEGIN are automatically rolled back. Tha…Implicit Rollback after Exceptions implicit_schemaExtensionsExtensionsEvent-trigger extension that automatically creates a schema when a table or view is created in a missing schema. ddl event-trigger schema pg_implicit_schema FeaturesFeatures · Extensions IMPORT FOREIGN SCHEMAManual ChaptersPG18IMPORT FOREIGN SCHEMA IMPORT FOREIGN SCHEMA — import table definitions from a foreign server Synopsis IMPORT FOREIGN SCHEMA remote_schema [ { LIMIT TO | EXCEPT } ( table_name [, ...] ) ] FRO…IMPORT FOREIGN SCHEMA