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ALTER COLLATION(7) PostgreSQL 12.3 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_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 also be a
direct or indirect member of 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 using collations provided by the ICU library, the ICU-specific version of the
collator is recorded in the system catalog when the collation object is created. 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 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
collator version and will make the warning go away. Note that this does not actually check
whether all affected objects have been rebuilt correctly.
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 12.3 2020 ALTER COLLATION(7)
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