<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/reindex.sgml,v 1.7 2001/11/25 01:11:36 tgl Exp $
Postgres documentation
-->

<refentry id="SQL-REINDEX">
 <refmeta>
  <refentrytitle id="SQL-REINDEX-TITLE">
   REINDEX
  </refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>
 <refnamediv>
  <refname>
   REINDEX
  </refname>
  <refpurpose>
   rebuild corrupted indexes
  </refpurpose>
 </refnamediv>
 <refsynopsisdiv>
  <refsynopsisdivinfo>
   <date>2000-03-30</date>
  </refsynopsisdivinfo>
  <synopsis>
REINDEX { TABLE | DATABASE | INDEX } <replaceable class="PARAMETER">name</replaceable> [ FORCE ]
  </synopsis>
  
  <refsect2 id="R2-SQL-REINDEX-1">
   <refsect2info>
    <date>2000-03-30</date>
   </refsect2info>
   <title>
    Inputs
   </title>
   <para>

    <variablelist>
     <varlistentry>
      <term>TABLE</term>
      <listitem>
       <para>
	Recreate all indexes of a specified table.
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term>DATABASE</term>
      <listitem>
       <para>
	Recreate all system indexes of a specified database.
	(User-table indexes are not included.)
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term>INDEX</term>
      <listitem>
       <para>
	Recreate a specified index.
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term><replaceable class="PARAMETER">name</replaceable></term>
      <listitem>
       <para>
	The name of the specific table/database/index to be be reindexed.
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term>FORCE</term>
      <listitem>
       <para>
	Force rebuild of system indexes.  Without this keyword
	<command>REINDEX</> skips system indexes that are not marked invalid.
	FORCE is irrelevant for <command>REINDEX INDEX</>, or when reindexing
	user indexes.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>
  
  <refsect2 id="R2-SQL-REINDEX-2">
   <refsect2info>
    <date>2000-03-30</date>
   </refsect2info>
   <title>
    Outputs
   </title>
   <para>

    <variablelist>
     <varlistentry>
      <term><computeroutput>
REINDEX
       </computeroutput></term>
      <listitem>
       <para>
	Message returned if the table is successfully reindexed.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>
 </refsynopsisdiv>

 <refsect1 id="R1-SQL-REINDEX-1">
  <refsect1info>
   <date>2000-03-30</date>
  </refsect1info>
  <title>
   Description
  </title>
  <para>
   <command>REINDEX</command> is used to rebuild corrupted indexes.
   Although in theory this should never be necessary, in practice
   indexes may become corrupted due to software bugs or hardware
   failures.  <command>REINDEX</command> provides a recovery method.
  </para>

  <para>
    If you suspect corruption of an index on a user table, you can
    simply rebuild that index, or all indexes on the table, using
    <command>REINDEX INDEX</command> or <command>REINDEX TABLE</command>.
  </para>

  <note>
   <para>
    Another approach to dealing with a corrupted user-table index is
    just to drop and recreate it.  This may in fact be preferable if
    you would like to maintain some semblance of normal operation on
    the table meanwhile.  <command>REINDEX</> acquires exclusive lock
    on the table, while <command>CREATE INDEX</> only locks out writes
    not reads of the table.
   </para>
  </note>

  <para>
   Things are more difficult if you need to recover from corruption of an
   index on a system table.  In this case it's important for the backend
   doing the recovery to not have used any of the suspect indexes itself.
   (Indeed, in this sort of scenario you may find that backends are
   crashing immediately at startup, due to reliance on the corrupted
   indexes.)  To recover safely, the postmaster must be shut down and a
   stand-alone Postgres backend must be started instead, giving it
   the command-line options -O and -P (these options allow system table
   modifications and prevent use of system indexes, respectively).  Then
   issue <command>REINDEX INDEX</>, <command>REINDEX TABLE</>, or
   <command>REINDEX DATABASE</> depending on how much you want to reconstruct.
   If in doubt, use <command>REINDEX DATABASE FORCE</> to force reconstruction
   of all system indexes in the database.  Then quit the standalone backend
   and restart the postmaster.
  </para>

  <para>
   Since this is likely the only situation when most people will ever use
   a standalone backend, some usage notes might be in order:

   <itemizedlist>
    <listitem>
     <para>
      Start the backend with a command like
<screen>
<userinput>postgres -D $PGDATA -O -P my_database</userinput>
</screen>
      Provide the correct path to the database area with <option>-D</>, or
      make sure that the environment variable <envar>PGDATA</> is set.
      Also specify the name of the particular database you want to work in.
     </para>
    </listitem>

    <listitem>
     <para>
      You can issue any SQL command, not only <command>REINDEX</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Be aware that the standalone backend treats newline as the command
      entry terminator; there is no intelligence about semicolons,
      as there is in <application>psql</>.  To continue a command
      across multiple lines, you must type backslash just before each
      newline except the last one.
      Also, you won't have any of the conveniences of readline processing
      (no command history, for example).
     </para>
    </listitem>

    <listitem>
     <para>
      To quit the backend, type EOF (control-D, usually).
     </para>
    </listitem>

   </itemizedlist>

   See the <xref linkend="app-postgres"> reference page for more information.
  </para>
 </refsect1>

 <refsect1 id="R1-SQL-REINDEX-2">
  <title>
   Usage
  </title>
  <para>
   Recreate the indexes on the table <literal>mytable</literal>:

   <programlisting>
     REINDEX TABLE mytable;
   </programlisting>
  </para>

  <para>
   Rebuild a single index:

   <programlisting>
    REINDEX INDEX my_index;
   </programlisting>
  </para>

  <para>
   Rebuild all system indexes (this will only work in a standalone backend):

   <programlisting>
    REINDEX DATABASE my_database FORCE;
   </programlisting>
  </para>
 </refsect1>
 
 <refsect1 id="R1-SQL-REINDEX-3">
  <title>
   Compatibility
  </title>
  
  <refsect2 id="R2-SQL-REINDEX-4">
   <refsect2info>
    <date>2000-03-30</date>
   </refsect2info>
   <title>
    SQL92
   </title>
   <para>
    There is no <command>REINDEX</command> in <acronym>SQL92</acronym>.
   </para>
  </refsect2>
 </refsect1>
</refentry>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
sgml-parent-document:nil
sgml-default-dtd-file:"../reference.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:"/usr/lib/sgml/catalog"
sgml-local-ecat-files:nil
End:
-->
