<!--
doc/src/sgml/ref/alter_index.sgml
PostgreSQL documentation
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<refentry id="sql-alterindex">
 <indexterm zone="sql-alterindex">
  <primary>ALTER INDEX</primary>
 </indexterm>

 <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>

 <refsynopsisdiv>
<synopsis>
ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RENAME TO <replaceable class="parameter">new_name</replaceable>
ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET TABLESPACE <replaceable class="parameter">tablespace_name</replaceable>
ALTER INDEX <replaceable class="parameter">name</replaceable> ATTACH PARTITION <replaceable class="parameter">index_name</replaceable>
ALTER INDEX <replaceable class="parameter">name</replaceable> [ NO ] DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable>
ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )
ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RESET ( <replaceable class="parameter">storage_parameter</replaceable> [, ... ] )
ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ALTER [ COLUMN ] <replaceable class="parameter">column_number</replaceable>
    SET STATISTICS <replaceable class="parameter">integer</replaceable>
ALTER INDEX ALL IN TABLESPACE <replaceable class="parameter">name</replaceable> [ OWNED BY <replaceable class="parameter">role_name</replaceable> [, ... ] ]
    SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable> [ NOWAIT ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>ALTER INDEX</command> changes the definition of an existing index.
   There are several subforms described below. Note that the lock level required
   may differ for each subform. An <literal>ACCESS EXCLUSIVE</literal> lock is held
   unless explicitly noted. When multiple subcommands are listed, the lock
   held will be the strictest one required from any subcommand.

  <variablelist>

   <varlistentry>
    <term><literal>RENAME</literal></term>
    <listitem>
     <para>
      The <literal>RENAME</literal> form changes the name of the index.
      If the index is associated with a table constraint (either
      <literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>,
      or <literal>EXCLUDE</literal>), the constraint is renamed as well.
      There is no effect on the stored data.
     </para>
     <para>
      Renaming an index acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
      lock.
     </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.
      To change the tablespace of an index, you must own the index and have
      <literal>CREATE</literal> privilege on the new tablespace.
      All indexes in the current database in a tablespace can be moved by using
      the <literal>ALL IN TABLESPACE</literal> form, which will lock all
      indexes to be moved and then move each one.  This form also supports
      <literal>OWNED BY</literal>, which will only move indexes owned by the
      roles specified.  If the <literal>NOWAIT</literal> option is specified
      then the command will fail if it is unable to acquire all of the locks
      required immediately.  Note that system catalogs will not be moved by
      this command, use <command>ALTER DATABASE</command> or explicit
      <command>ALTER INDEX</command> invocations