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ALTER COLLATION(7)	 PostgreSQL 17.5 Documentation	    ALTER COLLATION(7)

NAME
       ALTER_COLLATION - change	the definition of a collation

SYNOPSIS
       ALTER COLLATION name REFRESH VERSION

       ALTER COLLATION name RENAME TO new_name
       ALTER COLLATION name OWNER TO { new_owner | CURRENT_ROLE	| CURRENT_USER | SESSION_USER }
       ALTER COLLATION name SET	SCHEMA new_schema

DESCRIPTION
       ALTER COLLATION changes the definition of a collation.

       You must	own the	collation to use ALTER COLLATION. To alter the owner,
       you must	be able	to SET ROLE to the new owning role, and	that role must
       have CREATE privilege on	the collation's	schema.	(These restrictions
       enforce that altering the owner doesn't do anything you couldn't	do by
       dropping	and recreating the collation. However, a superuser can alter
       ownership of any	collation anyway.)

PARAMETERS
       name
	   The name (optionally	schema-qualified) of an	existing collation.

       new_name
	   The new name	of the collation.

       new_owner
	   The new owner of the	collation.

       new_schema
	   The new schema for the collation.

       REFRESH VERSION
	   Update the collation's version. See Notes below.

NOTES
       When a collation	object is created, the provider-specific version of
       the collation is	recorded in the	system catalog.	When the collation is
       used, the current version is checked against the	recorded version, and
       a warning is issued when	there is a mismatch, for example:

	   WARNING:  collation "xx-x-icu" has version mismatch
	   DETAIL:  The	collation in the database was created using version 1.2.3.4, but the operating system provides version 2.3.4.5.
	   HINT:  Rebuild all objects affected by this collation and run ALTER COLLATION pg_catalog."xx-x-icu" REFRESH VERSION,	or build PostgreSQL with the right library version.

       A change	in collation definitions can lead to corrupt indexes and other
       problems	because	the database system relies on stored objects having a
       certain sort order. Generally, this should be avoided, but it can
       happen in legitimate circumstances, such	as when	upgrading the
       operating system	to a new major version or when using pg_upgrade	to
       upgrade to server binaries linked with a	newer version of ICU. When
       this happens, all objects depending on the collation should be rebuilt,
       for example, using REINDEX. When	that is	done, the collation version
       can be refreshed	using the command ALTER	COLLATION ... REFRESH VERSION.
       This will update	the system catalog to record the current collation
       version and will	make the warning go away. Note that this does not
       actually	check whether all affected objects have	been rebuilt
       correctly.

       When using collations provided by libc, version information is recorded
       on systems using	the GNU	C library (most	Linux systems),	FreeBSD	and
       Windows.	When using collations provided by ICU, the version information
       is provided by the ICU library and is available on all platforms.

	   Note

	   When	using the GNU C	library	for collations,	the C library's
	   version is used as a	proxy for the collation	version. Many Linux
	   distributions change	collation definitions only when	upgrading the
	   C library, but this approach	is imperfect as	maintainers are	free
	   to back-port	newer collation	definitions to older C library
	   releases.

	   When	using Windows for collations, version information is only
	   available for collations defined with BCP 47	language tags such as
	   en-US.

       For the database	default	collation, there is an analogous command ALTER
       DATABASE	... REFRESH COLLATION VERSION.

       The following query can be used to identify all collations in the
       current database	that need to be	refreshed and the objects that depend
       on them:

	   SELECT pg_describe_object(refclassid, refobjid, refobjsubid)	AS "Collation",
		  pg_describe_object(classid, objid, objsubid) AS "Object"
	     FROM pg_depend d JOIN pg_collation	c
		  ON refclassid	= 'pg_collation'::regclass AND refobjid	= c.oid
	     WHERE c.collversion <> pg_collation_actual_version(c.oid)
	     ORDER BY 1, 2;

EXAMPLES
       To rename the collation de_DE to	german:

	   ALTER COLLATION "de_DE" RENAME TO german;

       To change the owner of the collation en_US to joe:

	   ALTER COLLATION "en_US" OWNER TO joe;

COMPATIBILITY
       There is	no ALTER COLLATION statement in	the SQL	standard.

SEE ALSO
       CREATE COLLATION	(CREATE_COLLATION(7)), DROP COLLATION
       (DROP_COLLATION(7))

PostgreSQL 17.5			     2025		    ALTER COLLATION(7)

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