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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> 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 (FILLFACTOR = <replaceable class="PARAMETER">fillfactor</replaceable>)
ALTER INDEX <replaceable class="PARAMETER">name</replaceable> RESET (FILLFACTOR)
</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" endterm="sql-createtablespace-title">.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET (FILLFACTOR)</literal></term>
    <listitem>
     <para>
      This form changes the index's fillfactor to the specified percentage.
      Index structure is not modified immediately; use <literal>REINDEX</literal>
      to ensure reflection of the change.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>RESET (FILLFACTOR)</literal></term>
    <listitem>
     <para>
      This form changes the index's fillfactor to the default value.
     </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>
        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>

    </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>
    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>

 </refsect1>

 <refsect1>
  <title>Compatibility</title>

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

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