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<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/alter_index.sgml,v 1.15 2010/04/03 07:22:56 petere Exp $
PostgreSQL documentation
-->
<refentry id="SQL-ALTERINDEX">
<refmeta>
<refentrytitle>ALTER INDEX</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>ALTER INDEX</refname>
<refpurpose>change the definition of an index</refpurpose>
</refnamediv>
<indexterm zone="sql-alterindex">
<primary>ALTER INDEX</primary>
</indexterm>
<refsynopsisdiv>
<synopsis>
ALTER INDEX <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
ALTER INDEX <replaceable class="PARAMETER">name</replaceable> SET TABLESPACE <replaceable class="PARAMETER">tablespace_name</replaceable>
ALTER INDEX <replaceable class="PARAMETER">name</replaceable> SET ( <replaceable class="PARAMETER">storage_parameter</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )
ALTER INDEX <replaceable class="PARAMETER">name</replaceable> RESET ( <replaceable class="PARAMETER">storage_parameter</replaceable> [, ... ] )
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>ALTER INDEX</command> changes the definition of an existing index.
There are several subforms:
<variablelist>
<varlistentry>
<term><literal>RENAME</literal></term>
<listitem>
<para>
The <literal>RENAME</literal> form changes the name of the index.
There is no effect on the stored data.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>SET TABLESPACE</literal></term>
<listitem>
<para>
This form changes the index's tablespace to the specified tablespace and
moves the data file(s) associated with the index to the new tablespace.
See also
<xref linkend="SQL-CREATETABLESPACE">.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>SET ( <replaceable class="PARAMETER">storage_parameter</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )</literal></term>
<listitem>
<para>
This form changes one or more index-method-specific storage parameters
for the index. See
<xref linkend="SQL-CREATEINDEX">
for details on the available parameters. Note that the index contents
will not be modified immediately by this command; depending on the
parameter you might need to rebuild the index with
<xref linkend="SQL-REINDEX">
to get the desired effects.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>RESET ( <replaceable class="PARAMETER">storage_parameter</replaceable> [, ... ] )</literal></term>
<listitem>
<para>
This form resets one or more index-method-specific storage parameters to
their defaults. As with <literal>SET</>, a <literal>REINDEX</literal>
might be needed to update the index entirely.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
The name (possibly schema-qualified) of an existing index to
alter.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">new_name</replaceable></term>
<listitem>
<para>
The new name for the index.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">tablespace_name</replaceable></term>
<listitem>
<para>
The tablespace to which the index will be moved.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">storage_parameter</replaceable></term>
<listitem>
<para>
The name of an index-method-specific storage parameter.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">value</replaceable></term>
<listitem>
<para>
The new value for an index-method-specific storage parameter.
This might be a number or a word depending on the parameter.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
These operations are also possible using
<xref linkend="SQL-ALTERTABLE">.
<command>ALTER INDEX</> is in fact just an alias for the forms
of <command>ALTER TABLE</> that apply to indexes.
</para>
<para>
There was formerly an <command>ALTER INDEX OWNER</> variant, but
this is now ignored (with a warning). An index cannot have an owner
different from its table's owner. Changing the table's owner
automatically changes the index as well.
</para>
<para>
Changing any part of a system catalog index is not permitted.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
To rename an existing index:
<programlisting>
ALTER INDEX distributors RENAME TO suppliers;
</programlisting>
</para>
<para>
To move an index to a different tablespace:
<programlisting>
ALTER INDEX distributors SET TABLESPACE fasttablespace;
</programlisting>
</para>
<para>
To change an index's fill factor (assuming that the index method
supports it):
<programlisting>
ALTER INDEX distributors SET (fillfactor = 75);
REINDEX INDEX distributors;
</programlisting>
</para>
</refsect1>
<refsect1>
<title>Compatibility</title>
<para>
<command>ALTER INDEX</> is a <productname>PostgreSQL</productname>
extension.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-createindex"></member>
<member><xref linkend="sql-reindex"></member>
</simplelist>
</refsect1>
</refentry>
|
