ALTER_COLLATION(7)

1ALTER COLLATION(7)       PostgreSQL 15.4 Documentation      ALTER COLLATION(7)
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NAME

6       ALTER_COLLATION - change the definition of a collation
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SYNOPSIS

9       ALTER COLLATION name REFRESH VERSION
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11       ALTER COLLATION name RENAME TO new_name
12       ALTER COLLATION name OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
13       ALTER COLLATION name SET SCHEMA new_schema
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DESCRIPTION

16       ALTER COLLATION changes the definition of a collation.
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18       You must own the collation to use ALTER COLLATION. To alter the owner,
19       you must also be a direct or indirect member of the new owning role,
20       and that role must have CREATE privilege on the collation's schema.
21       (These restrictions enforce that altering the owner doesn't do anything
22       you couldn't do by dropping and recreating the collation. However, a
23       superuser can alter ownership of any collation anyway.)
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PARAMETERS

26       name
27           The name (optionally schema-qualified) of an existing collation.
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29       new_name
30           The new name of the collation.
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32       new_owner
33           The new owner of the collation.
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35       new_schema
36           The new schema for the collation.
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38       REFRESH VERSION
39           Update the collation's version. See Notes below.
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NOTES

42       When a collation object is created, the provider-specific version of
43       the collation is recorded in the system catalog. When the collation is
44       used, the current version is checked against the recorded version, and
45       a warning is issued when there is a mismatch, for example:
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47           WARNING:  collation "xx-x-icu" has version mismatch
48           DETAIL:  The collation in the database was created using version 1.2.3.4, but the operating system provides version 2.3.4.5.
49           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.
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51       A change in collation definitions can lead to corrupt indexes and other
52       problems because the database system relies on stored objects having a
53       certain sort order. Generally, this should be avoided, but it can
54       happen in legitimate circumstances, such as when upgrading the
55       operating system to a new major version or when using pg_upgrade to
56       upgrade to server binaries linked with a newer version of ICU. When
57       this happens, all objects depending on the collation should be rebuilt,
58       for example, using REINDEX. When that is done, the collation version
59       can be refreshed using the command ALTER COLLATION ... REFRESH VERSION.
60       This will update the system catalog to record the current collation
61       version and will make the warning go away. Note that this does not
62       actually check whether all affected objects have been rebuilt
63       correctly.
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65       When using collations provided by libc, version information is recorded
66       on systems using the GNU C library (most Linux systems), FreeBSD and
67       Windows. When using collations provided by ICU, the version information
68       is provided by the ICU library and is available on all platforms.
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70           Note
71           When using the GNU C library for collations, the C library's
72           version is used as a proxy for the collation version. Many Linux
73           distributions change collation definitions only when upgrading the
74           C library, but this approach is imperfect as maintainers are free
75           to back-port newer collation definitions to older C library
76           releases.
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78           When using Windows for collations, version information is only
79           available for collations defined with BCP 47 language tags such as
80           en-US.
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82       For the database default collation, there is an analogous command ALTER
83       DATABASE ... REFRESH COLLATION VERSION.
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85       The following query can be used to identify all collations in the
86       current database that need to be refreshed and the objects that depend
87       on them:
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89           SELECT pg_describe_object(refclassid, refobjid, refobjsubid) AS "Collation",
90                  pg_describe_object(classid, objid, objsubid) AS "Object"
91             FROM pg_depend d JOIN pg_collation c
92                  ON refclassid = 'pg_collation'::regclass AND refobjid = c.oid
93             WHERE c.collversion <> pg_collation_actual_version(c.oid)
94             ORDER BY 1, 2;
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EXAMPLES

97       To rename the collation de_DE to german:
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99           ALTER COLLATION "de_DE" RENAME TO german;
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101       To change the owner of the collation en_US to joe:
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103           ALTER COLLATION "en_US" OWNER TO joe;
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COMPATIBILITY

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