<term><literal>REFRESH VERSION</literal></term>

<listitem>

<para>

Updated the collation version.

Update the collation's version.

See <xref linkend="sql-altercollation-notes"

endterm="sql-altercollation-notes-title"> below.

</para>

<para>

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 isthenused, the current version is

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:

<screen>

WARNING:ICU collator version mismatch

DETAIL: The database was created using version 1.2.3.4, thelibrary 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 rightversion of ICU.

WARNING:collation "xx-x-icu" has version mismatch

DETAIL: Thecollation in thedatabase was created using version 1.2.3.4,buttheoperating 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 rightlibrary version.

</screen>

A change in collation definitions can lead to corrupt indexes and other

problemswhere the database system relies on stored objects having a

problemsbecause 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 <command>pg_upgrade</command> to upgrade to server binaries linked

<para>

Specifies the provider to use for locale services associated with this

collation. Possible values

are: <literal>icu</literal>,<indexterm><primary>ICU</></> <literal>libc</literal>.

are: <literal>icu</literal>,<indexterm><primary>ICU</></>

<literal>libc</literal>.

<literal>libc</literal> is the default.

The available choices depend on the operating system and build options.

</para>

</listitem>