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<refentry id="SQL-ALTERINDEX">
 <refmeta>
  <refentrytitle id="sql-alterindex-title">ALTER INDEX</refentrytitle>
  <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> 
    <replaceable class="PARAMETER">action</replaceable> [, ... ]
ALTER INDEX <replaceable class="PARAMETER">name</replaceable>
    RENAME TO <replaceable class="PARAMETER">new_name</replaceable>

where <replaceable class="PARAMETER">action</replaceable> is one of:

    OWNER TO <replaceable class="PARAMETER">new_owner</replaceable>
    SET TABLESPACE <replaceable class="PARAMETER">indexspace_name</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>OWNER</literal></term>
    <listitem>
     <para>
      This form changes the owner of the index to the
      specified user.  This can only be done by a superuser.
     </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" endterm="sql-createtablespace-title">.
     </para>
    </listitem>
   </varlistentry>

   <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>

  </variablelist>
  </para>

  <para>
   All the actions except <literal>RENAME</literal> can be combined into
   a list of multiple alterations to apply in parallel.
  </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>
	New name for the index.
       </para>
      </listitem>
     </varlistentry>


     <varlistentry>
      <term><replaceable class="PARAMETER">new_owner</replaceable></term>
      <listitem>
       <para>
	The user name of the new owner of the index.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="PARAMETER">tablespace_name</replaceable></term>
      <listitem>
       <para>
	The tablespace name to which the index will be moved.
       </para>
      </listitem>
     </varlistentry>

    </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

   <para>
    These operations are also possible using
    <xref linkend="SQL-ALTERTABLE" endterm="SQL-ALTERTABLE-TITLE">.
    <command>ALTER INDEX</> is in fact just an alias for the forms
    of <command>ALTER TABLE</> that apply to indexes.
   </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 a index to a different tablespace:
<programlisting>
ALTER INDEX distributors SET TABLESPACE fasttablespace;
</programlisting>
  </para>

 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <command>ALTER INDEX</> is a <productname>PostgreSQL</productname>
   extension.
  </para>
 </refsect1>
</refentry>

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