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 <!--
 doc/src/sgml/ref/vacuum.sgml
 PostgreSQL documentation
 -->

 <refentry id="sql-vacuum">
  <indexterm zone="sql-vacuum">
   <primary>VACUUM</primary>
  </indexterm>

  <refmeta>
   <refentrytitle>VACUUM</refentrytitle>
   <manvolnum>7</manvolnum>
   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  </refmeta>

  <refnamediv>
   <refname>VACUUM</refname>
   <refpurpose>garbage-collect and optionally analyze a database</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
 <synopsis>
 VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <replaceable class="parameter">table_and_columns</replaceable> [, ...] ]
 VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="parameter">table_and_columns</replaceable> [, ...] ]

 <phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>

     FULL [ <replaceable class="parameter">boolean</replaceable> ]
     FREEZE [ <replaceable class="parameter">boolean</replaceable> ]
     VERBOSE [ <replaceable class="parameter">boolean</replaceable> ]
     ANALYZE [ <replaceable class="parameter">boolean</replaceable> ]
     DISABLE_PAGE_SKIPPING [ <replaceable class="parameter">boolean</replaceable> ]
     SKIP_LOCKED [ <replaceable class="parameter">boolean</replaceable> ]
     INDEX_CLEANUP { AUTO | ON | OFF }
     PROCESS_TOAST [ <replaceable class="parameter">boolean</replaceable> ]
     TRUNCATE [ <replaceable class="parameter">boolean</replaceable> ]
     PARALLEL <replaceable class="parameter">integer</replaceable>

 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>

     <replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
 </synopsis>
  </refsynopsisdiv>

  <refsect1>
   <title>Description</title>

   <para>
    <command>VACUUM</command> reclaims storage occupied by dead tuples.
    In normal <productname>PostgreSQL</productname> operation, tuples that
    are deleted or obsoleted by an update are not physically removed from
    their table; they remain present until a <command>VACUUM</command> is
    done.  Therefore it's necessary to do <command>VACUUM</command>
    periodically, especially on frequently-updated tables.
   </para>

   <para>
    Without a <replaceable class="parameter">table_and_columns</replaceable>
    list, <command>VACUUM</command> processes every table and materialized view
    in the current database that the current user has permission to vacuum.
    With a list, <command>VACUUM</command> processes only those table(s).
   </para>

   <para>
    <command>VACUUM ANALYZE</command> performs a <command>VACUUM</command>
    and then an <command>ANALYZE</command> for each selected table.  This
    is a handy combination form for routine maintenance scripts.  See
    <xref linkend="sql-analyze"/>
    for more details about its processing.
   </para>

   <para>
    Plain <command>VACUUM</command> (without <literal>FULL</literal>) simply reclaims
    space and makes it
    available for re-use.  This form of the command can operate in parallel
    with normal reading and writing of the table, as an exclusive lock
    is not obtained.  However, extra space is not returned to the operating
    system (in most cases); it's just kept available for re-use within the
    same table.  It also allows us to leverage multiple CPUs in order to process
    indexes.  This feature is known as <firstterm>parallel vacuum</firstterm>.
    To disable this feature, one can use <literal>PARALLEL</literal> option and
    specify parallel workers as zero.  <command>VACUUM FULL</command> rewrites
    the entire contents of the table into a new disk file with no extra space,
    allowing unused space to be returned to the operating system.  This form is
    much slower and requires an <literal>ACCESS EXCLUSIVE</literal> lock on
    each table while it is being processed.
   </para>

   <para>
    When the option list is surrounded by parentheses, the options can be
    written in any order.  Without parentheses, options must be specified
    in exactly the order shown above.
    The parenthesized syntax was added in
    <productname>PostgreSQL</productname> 9.0;  the unparenthesized
    syntax is deprecated.
   </para>
  </refsect1>

  <refsect1>
   <title>Parameters</title>

   <variablelist>
    <varlistentry>
     <term><literal>FULL</literal></term>
     <listitem>
      <para>
       Selects <quote>full</quote> vacuum, which can reclaim more
       space, but takes much longer and exclusively locks the table.
       This method also requires extra disk space, since it writes a
       new copy of the table and doesn't release the old copy until
       the operation is complete.  Usually this should only be used when a
       significant amount of space needs to be reclaimed from within the table.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>FREEZE</literal></term>
     <listitem>
      <para>
       Selects aggressive <quote>freezing</quote> of tuples.
       Specifying <literal>FREEZE</literal> is equivalent to performing
       <command>VACUUM</command> with the
       <xref linkend="guc-vacuum-freeze-min-age"/> and
       <xref linkend="guc-vacuum-freeze-table-age"/> parameters
       set to zero.  Aggressive freezing is always performed when the
       table is rewritten, so this option is redundant when <literal>FULL</literal>
       is specified.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>VERBOSE</literal></term>
     <listitem>
      <para>
       Prints a detailed vacuum activity report for each table.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>ANALYZE</literal></term>
     <listitem>
      <para>
       Updates statistics used by the planner to determine the most
       efficient way to execute a query.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>DISABLE_PAGE_SKIPPING</literal></term>
     <listitem>
      <para>
       Normally, <command>VACUUM</command> will skip pages based on the <link
       linkend="vacuum-for-visibility-map">visibility map</link>.  Pages where
       all tuples are known to be frozen can always be skipped, and those
       where all tuples are known to be visible to all transactions may be
       skipped except when performing an aggressive vacuum.  Furthermore,
       except when performing an aggressive vacuum, some pages may be skipped
       in order to avoid waiting for other sessions to finish using them.
       This option disables all page-skipping behavior, and is intended to
       be used only when the contents of the visibility map are
       suspect, which should happen only if there is a hardware or software
       issue causing database corruption.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>SKIP_LOCKED</literal></term>
     <listitem>
      <para>
       Specifies that <command>VACUUM</command> should not wait for any
       conflicting locks to be released when beginning work on a relation:
       if a relation cannot be locked immediately without waiting, the relation
       is skipped.  Note that even with this option,
       <command>VACUUM</command> may still block when opening the relation's
       indexes.  Additionally, <command>VACUUM ANALYZE</command> may still
       block when acquiring sample rows from partitions, table inheritance
       children, and some types of foreign tables.  Also, while
       <command>VACUUM</command> ordinarily processes all partitions of
       specified partitioned tables, this option will cause
       <command>VACUUM</command> to skip all partitions if there is a
       conflicting lock on the partitioned table.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>INDEX_CLEANUP</literal></term>
     <listitem>
      <para>
       Normally, <command>VACUUM</command> will skip index vacuuming
       when there are very few dead tuples in the table.  The cost of
       processing all of the table's indexes is expected to greatly
       exceed the benefit of removing dead index tuples when this
       happens.  This option can be used to force
       <command>VACUUM</command> to process indexes when there are more
       than zero dead tuples.  The default is <literal>AUTO</literal>,
       which allows <command>VACUUM</command> to skip index vacuuming
       when appropriate.  If <literal>INDEX_CLEANUP</literal> is set to
       <literal>ON</literal>, <command>VACUUM</command> will
       conservatively remove all dead tuples from indexes.  This may be
       useful for backwards compatibility with earlier releases of
       <productname>PostgreSQL</productname> where this was the
       standard behavior.
      </para>
      <para>
       <literal>INDEX_CLEANUP</literal> can also be set to
       <literal>OFF</literal> to force <command>VACUUM</command> to
       <emphasis>always</emphasis> skip index vacuuming, even when
       there are many dead tuples in the table.  This may be useful
       when it is necessary to make <command>VACUUM</command> run as
       quickly as possible to avoid imminent transaction ID wraparound
       (see <xref linkend="vacuum-for-wraparound"/>).  However, the
       wraparound failsafe mechanism controlled by <xref
        linkend="guc-vacuum-failsafe-age"/>  will generally trigger
       automatically to avoid transaction ID wraparound failure, and
       should be preferred.  If index cleanup is not performed
       regularly, performance may suffer, because as the table is
       modified indexes will accumulate dead tuples and the table
       itself will accumulate dead line pointers that cannot be removed
       until index cleanup is completed.
      </para>
      <para>
       This option has no effect for tables that have no index and is
       ignored if the <literal>FULL</literal> option is used.  It also
       has no effect on the transaction ID wraparound failsafe
       mechanism.  When triggered it will skip index vacuuming, even
       when <literal>INDEX_CLEANUP</literal> is set to
       <literal>ON</literal>.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>PROCESS_TOAST</literal></term>
     <listitem>
      <para>
       Specifies that <command>VACUUM</command> should attempt to process the
       corresponding <literal>TOAST</literal> table for each relation, if one
       exists. This is usually the desired behavior and is the default.
       Setting this option to false may be useful when it is only necessary to
       vacuum the main relation. This option is required when the
       <literal>FULL</literal> option is used.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TRUNCATE</literal></term>
     <listitem>
      <para>
       Specifies that <command>VACUUM</command> should attempt to
       truncate off any empty pages at the end of the table and allow
       the disk space for the truncated pages to be returned to
       the operating system. This is normally the desired behavior
       and is the default unless the <literal>vacuum_truncate</literal>
       option has been set to false for the table to be vacuumed.
       Setting this option to false may be useful to avoid
       <literal>ACCESS EXCLUSIVE</literal> lock on the table that
       the truncation requires. This option is ignored if the
       <literal>FULL</literal> option is used.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>PARALLEL</literal></term>
     <listitem>
      <para>
       Perform index vacuum and index cleanup phases of <command>VACUUM</command>
       in parallel using <replaceable class="parameter">integer</replaceable>
       background workers (for the details of each vacuum phase, please
       refer to <xref linkend="vacuum-phases"/>).  The number of workers used
       to perform the operation is equal to the number of indexes on the
       relation that support parallel vacuum which is limited by the number of
       workers specified with <literal>PARALLEL</literal> option if any which is
       further limited by <xref linkend="guc-max-parallel-maintenance-workers"/>.
       An index can participate in parallel vacuum if and only if the size of the
       index is more than <xref linkend="guc-min-parallel-index-scan-size"/>.
       Please note that it is not guaranteed that the number of parallel workers
       specified in <replaceable class="parameter">integer</replaceable> will be
       used during execution.  It is possible for a vacuum to run with fewer
       workers than specified, or even with no workers at all.  Only one worker
       can be used per index.  So parallel workers are launched only when there
       are at least <literal>2</literal> indexes in the table.  Workers for
       vacuum are launched before the start of each phase and exit at the end of
       the phase.  These behaviors might change in a future release.  This
       option can't be used with the <literal>FULL</literal> option.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">boolean</replaceable></term>
     <listitem>
      <para>
       Specifies whether the selected option should be turned on or off.
       You can write <literal>TRUE</literal>, <literal>ON</literal>, or
       <literal>1</literal> to enable the option, and <literal>FALSE</literal>,
       <literal>OFF</literal>, or <literal>0</literal> to disable it.  The
       <replaceable class="parameter">boolean</replaceable> value can also
       be omitted, in which case <literal>TRUE</literal> is assumed.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">integer</replaceable></term>
     <listitem>
      <para>
       Specifies a non-negative integer value passed to the selected option.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">table_name</replaceable></term>
     <listitem>
      <para>
       The name (optionally schema-qualified) of a specific table or
       materialized view to vacuum.  If the specified table is a partitioned
       table, all of its leaf partitions are vacuumed.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">column_name</replaceable></term>
     <listitem>
      <para>
       The name of a specific column to analyze. Defaults to all columns.
       If a column list is specified, <literal>ANALYZE</literal> must also be
       specified.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </refsect1>

  <refsect1>
   <title>Outputs</title>

    <para>
     When <literal>VERBOSE</literal> is specified, <command>VACUUM</command> emits
     progress messages to indicate which table is currently being
     processed.  Various statistics about the tables are printed as well.
    </para>
  </refsect1>

  <refsect1>
   <title>Notes</title>

    <para>
     To vacuum a table, one must ordinarily be the table's owner or a
     superuser.  However, database owners are allowed to
     vacuum all tables in their databases, except shared catalogs.
     (The restriction for shared catalogs means that a true database-wide
     <command>VACUUM</command> can only be performed by a superuser.)
     <command>VACUUM</command> will skip over any tables that the calling user
     does not have permission to vacuum.
    </para>

    <para>
     <command>VACUUM</command> cannot be executed inside a transaction block.
    </para>

    <para>
     For tables with <acronym>GIN</acronym> indexes, <command>VACUUM</command> (in
     any form) also completes any pending index insertions, by moving pending
     index entries to the appropriate places in the main <acronym>GIN</acronym> index
     structure.  See <xref linkend="gin-fast-update"/> for details.
    </para>

    <para>
     We recommend that active production databases be
     vacuumed frequently (at least nightly), in order to
     remove dead rows. After adding or deleting a large number
     of rows, it might be a good idea to issue a <command>VACUUM
     ANALYZE</command> command for the affected table. This will update the
     system catalogs with
     the results of all recent changes, and allow the
     <productname>PostgreSQL</productname> query planner to make better
     choices in planning queries.
    </para>

    <para>
     The <option>FULL</option> option is not recommended for routine use,
     but might be useful in special cases.  An example is when you have deleted
     or updated most of the rows in a table and would like the table to
     physically shrink to occupy less disk space and allow faster table
     scans. <command>VACUUM FULL</command> will usually shrink the table
     more than a plain <command>VACUUM</command> would.
    </para>

    <para>
      The <option>PARALLEL</option> option is used only for vacuum purposes.
      If this option is specified with the <option>ANALYZE</option> option,
      it does not affect <option>ANALYZE</option>.
    </para>

    <para>
     <command>VACUUM</command> causes a substantial increase in I/O traffic,
     which might cause poor performance for other active sessions.  Therefore,
     it is sometimes advisable to use the cost-based vacuum delay feature.  For
     parallel vacuum, each worker sleeps in proportion to the work done by that
     worker.  See <xref linkend="runtime-config-resource-vacuum-cost"/> for
     details.
    </para>

    <para>
     <productname>PostgreSQL</productname> includes an <quote>autovacuum</quote>
     facility which can automate routine vacuum maintenance.  For more
     information about automatic and manual vacuuming, see
     <xref linkend="routine-vacuuming"/>.
    </para>
    <para>
     Each backend running <command>VACUUM</command> without the
     <literal>FULL</literal> option will report its progress in the
     <structname>pg_stat_progress_vacuum</structname> view. Backends running
     <command>VACUUM FULL</command> will instead report their progress in the
     <structname>pg_stat_progress_cluster</structname> view. See
     <xref linkend="vacuum-progress-reporting"/> and
     <xref linkend="cluster-progress-reporting"/> for details.
    </para>
  </refsect1>

  <refsect1>
   <title>Examples</title>

   <para>
    To clean a single table <literal>onek</literal>, analyze it for
    the optimizer and print a detailed vacuum activity report:

 <programlisting>
 VACUUM (VERBOSE, ANALYZE) onek;
 </programlisting></para>
  </refsect1>

  <refsect1>
   <title>Compatibility</title>

   <para>
    There is no <command>VACUUM</command> statement in the SQL standard.
   </para>
  </refsect1>

  <refsect1>
   <title>See Also</title>

   <simplelist type="inline">
    <member><xref linkend="app-vacuumdb"/></member>
    <member><xref linkend="runtime-config-resource-vacuum-cost"/></member>
    <member><xref linkend="autovacuum"/></member>
    <member><xref linkend="vacuum-progress-reporting"/></member>
    <member><xref linkend="cluster-progress-reporting"/></member>
   </simplelist>
  </refsect1>
 </refentry>
	<!--
	doc/src/sgml/ref/vacuum.sgml
	PostgreSQL documentation
	-->

	<refentry id="sql-vacuum">
	<indexterm zone="sql-vacuum">
	<primary>VACUUM</primary>
	</indexterm>

	<refmeta>
	<refentrytitle>VACUUM</refentrytitle>
	<manvolnum>7</manvolnum>
	<refmiscinfo>SQL - Language Statements</refmiscinfo>
	</refmeta>

	<refnamediv>
	<refname>VACUUM</refname>
	<refpurpose>garbage-collect and optionally analyze a database</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	<synopsis>
	VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <replaceable class="parameter">table_and_columns</replaceable> [, ...] ]
	VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="parameter">table_and_columns</replaceable> [, ...] ]

	<phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>

	FULL [ <replaceable class="parameter">boolean</replaceable> ]
	FREEZE [ <replaceable class="parameter">boolean</replaceable> ]
	VERBOSE [ <replaceable class="parameter">boolean</replaceable> ]
	ANALYZE [ <replaceable class="parameter">boolean</replaceable> ]
	DISABLE_PAGE_SKIPPING [ <replaceable class="parameter">boolean</replaceable> ]
	SKIP_LOCKED [ <replaceable class="parameter">boolean</replaceable> ]
	INDEX_CLEANUP { AUTO \| ON \| OFF }
	PROCESS_TOAST [ <replaceable class="parameter">boolean</replaceable> ]
	TRUNCATE [ <replaceable class="parameter">boolean</replaceable> ]
	PARALLEL <replaceable class="parameter">integer</replaceable>

	<phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>

	<replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
	</synopsis>
	</refsynopsisdiv>

	<refsect1>
	<title>Description</title>

	<para>
	<command>VACUUM</command> reclaims storage occupied by dead tuples.
	In normal <productname>PostgreSQL</productname> operation, tuples that
	are deleted or obsoleted by an update are not physically removed from
	their table; they remain present until a <command>VACUUM</command> is
	done. Therefore it's necessary to do <command>VACUUM</command>
	periodically, especially on frequently-updated tables.
	</para>

	<para>
	Without a <replaceable class="parameter">table_and_columns</replaceable>
	list, <command>VACUUM</command> processes every table and materialized view
	in the current database that the current user has permission to vacuum.
	With a list, <command>VACUUM</command> processes only those table(s).
	</para>

	<para>
	<command>VACUUM ANALYZE</command> performs a <command>VACUUM</command>
	and then an <command>ANALYZE</command> for each selected table. This
	is a handy combination form for routine maintenance scripts. See
	<xref linkend="sql-analyze"/>
	for more details about its processing.
	</para>

	<para>
	Plain <command>VACUUM</command> (without <literal>FULL</literal>) simply reclaims
	space and makes it
	available for re-use. This form of the command can operate in parallel
	with normal reading and writing of the table, as an exclusive lock
	is not obtained. However, extra space is not returned to the operating
	system (in most cases); it's just kept available for re-use within the
	same table. It also allows us to leverage multiple CPUs in order to process
	indexes. This feature is known as <firstterm>parallel vacuum</firstterm>.
	To disable this feature, one can use <literal>PARALLEL</literal> option and
	specify parallel workers as zero. <command>VACUUM FULL</command> rewrites
	the entire contents of the table into a new disk file with no extra space,
	allowing unused space to be returned to the operating system. This form is
	much slower and requires an <literal>ACCESS EXCLUSIVE</literal> lock on
	each table while it is being processed.
	</para>

	<para>
	When the option list is surrounded by parentheses, the options can be
	written in any order. Without parentheses, options must be specified
	in exactly the order shown above.
	The parenthesized syntax was added in
	<productname>PostgreSQL</productname> 9.0; the unparenthesized
	syntax is deprecated.
	</para>
	</refsect1>

	<refsect1>
	<title>Parameters</title>

	<variablelist>
	<varlistentry>
	<term><literal>FULL</literal></term>
	<listitem>
	<para>
	Selects <quote>full</quote> vacuum, which can reclaim more
	space, but takes much longer and exclusively locks the table.
	This method also requires extra disk space, since it writes a
	new copy of the table and doesn't release the old copy until
	the operation is complete. Usually this should only be used when a
	significant amount of space needs to be reclaimed from within the table.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>FREEZE</literal></term>
	<listitem>
	<para>
	Selects aggressive <quote>freezing</quote> of tuples.
	Specifying <literal>FREEZE</literal> is equivalent to performing
	<command>VACUUM</command> with the
	<xref linkend="guc-vacuum-freeze-min-age"/> and
	<xref linkend="guc-vacuum-freeze-table-age"/> parameters
	set to zero. Aggressive freezing is always performed when the
	table is rewritten, so this option is redundant when <literal>FULL</literal>
	is specified.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>VERBOSE</literal></term>
	<listitem>
	<para>
	Prints a detailed vacuum activity report for each table.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>ANALYZE</literal></term>
	<listitem>
	<para>
	Updates statistics used by the planner to determine the most
	efficient way to execute a query.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>DISABLE_PAGE_SKIPPING</literal></term>
	<listitem>
	<para>
	Normally, <command>VACUUM</command> will skip pages based on the <link
	linkend="vacuum-for-visibility-map">visibility map</link>. Pages where
	all tuples are known to be frozen can always be skipped, and those
	where all tuples are known to be visible to all transactions may be
	skipped except when performing an aggressive vacuum. Furthermore,
	except when performing an aggressive vacuum, some pages may be skipped
	in order to avoid waiting for other sessions to finish using them.
	This option disables all page-skipping behavior, and is intended to
	be used only when the contents of the visibility map are
	suspect, which should happen only if there is a hardware or software
	issue causing database corruption.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>SKIP_LOCKED</literal></term>
	<listitem>
	<para>
	Specifies that <command>VACUUM</command> should not wait for any
	conflicting locks to be released when beginning work on a relation:
	if a relation cannot be locked immediately without waiting, the relation
	is skipped. Note that even with this option,
	<command>VACUUM</command> may still block when opening the relation's
	indexes. Additionally, <command>VACUUM ANALYZE</command> may still
	block when acquiring sample rows from partitions, table inheritance
	children, and some types of foreign tables. Also, while
	<command>VACUUM</command> ordinarily processes all partitions of
	specified partitioned tables, this option will cause
	<command>VACUUM</command> to skip all partitions if there is a
	conflicting lock on the partitioned table.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>INDEX_CLEANUP</literal></term>
	<listitem>
	<para>
	Normally, <command>VACUUM</command> will skip index vacuuming
	when there are very few dead tuples in the table. The cost of
	processing all of the table's indexes is expected to greatly
	exceed the benefit of removing dead index tuples when this
	happens. This option can be used to force
	<command>VACUUM</command> to process indexes when there are more
	than zero dead tuples. The default is <literal>AUTO</literal>,
	which allows <command>VACUUM</command> to skip index vacuuming
	when appropriate. If <literal>INDEX_CLEANUP</literal> is set to
	<literal>ON</literal>, <command>VACUUM</command> will
	conservatively remove all dead tuples from indexes. This may be
	useful for backwards compatibility with earlier releases of
	<productname>PostgreSQL</productname> where this was the
	standard behavior.
	</para>
	<para>
	<literal>INDEX_CLEANUP</literal> can also be set to
	<literal>OFF</literal> to force <command>VACUUM</command> to
	<emphasis>always</emphasis> skip index vacuuming, even when
	there are many dead tuples in the table. This may be useful
	when it is necessary to make <command>VACUUM</command> run as
	quickly as possible to avoid imminent transaction ID wraparound
	(see <xref linkend="vacuum-for-wraparound"/>). However, the
	wraparound failsafe mechanism controlled by <xref
	linkend="guc-vacuum-failsafe-age"/> will generally trigger
	automatically to avoid transaction ID wraparound failure, and
	should be preferred. If index cleanup is not performed
	regularly, performance may suffer, because as the table is
	modified indexes will accumulate dead tuples and the table
	itself will accumulate dead line pointers that cannot be removed
	until index cleanup is completed.
	</para>
	<para>
	This option has no effect for tables that have no index and is
	ignored if the <literal>FULL</literal> option is used. It also
	has no effect on the transaction ID wraparound failsafe
	mechanism. When triggered it will skip index vacuuming, even
	when <literal>INDEX_CLEANUP</literal> is set to
	<literal>ON</literal>.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>PROCESS_TOAST</literal></term>
	<listitem>
	<para>
	Specifies that <command>VACUUM</command> should attempt to process the
	corresponding <literal>TOAST</literal> table for each relation, if one
	exists. This is usually the desired behavior and is the default.
	Setting this option to false may be useful when it is only necessary to
	vacuum the main relation. This option is required when the
	<literal>FULL</literal> option is used.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>TRUNCATE</literal></term>
	<listitem>
	<para>
	Specifies that <command>VACUUM</command> should attempt to
	truncate off any empty pages at the end of the table and allow
	the disk space for the truncated pages to be returned to
	the operating system. This is normally the desired behavior
	and is the default unless the <literal>vacuum_truncate</literal>
	option has been set to false for the table to be vacuumed.
	Setting this option to false may be useful to avoid
	<literal>ACCESS EXCLUSIVE</literal> lock on the table that
	the truncation requires. This option is ignored if the
	<literal>FULL</literal> option is used.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>PARALLEL</literal></term>
	<listitem>
	<para>
	Perform index vacuum and index cleanup phases of <command>VACUUM</command>
	in parallel using <replaceable class="parameter">integer</replaceable>
	background workers (for the details of each vacuum phase, please
	refer to <xref linkend="vacuum-phases"/>). The number of workers used
	to perform the operation is equal to the number of indexes on the
	relation that support parallel vacuum which is limited by the number of
	workers specified with <literal>PARALLEL</literal> option if any which is
	further limited by <xref linkend="guc-max-parallel-maintenance-workers"/>.
	An index can participate in parallel vacuum if and only if the size of the
	index is more than <xref linkend="guc-min-parallel-index-scan-size"/>.
	Please note that it is not guaranteed that the number of parallel workers
	specified in <replaceable class="parameter">integer</replaceable> will be
	used during execution. It is possible for a vacuum to run with fewer
	workers than specified, or even with no workers at all. Only one worker
	can be used per index. So parallel workers are launched only when there
	are at least <literal>2</literal> indexes in the table. Workers for
	vacuum are launched before the start of each phase and exit at the end of
	the phase. These behaviors might change in a future release. This
	option can't be used with the <literal>FULL</literal> option.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><replaceable class="parameter">boolean</replaceable></term>
	<listitem>
	<para>
	Specifies whether the selected option should be turned on or off.
	You can write <literal>TRUE</literal>, <literal>ON</literal>, or
	<literal>1</literal> to enable the option, and <literal>FALSE</literal>,
	<literal>OFF</literal>, or <literal>0</literal> to disable it. The
	<replaceable class="parameter">boolean</replaceable> value can also
	be omitted, in which case <literal>TRUE</literal> is assumed.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><replaceable class="parameter">integer</replaceable></term>
	<listitem>
	<para>
	Specifies a non-negative integer value passed to the selected option.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><replaceable class="parameter">table_name</replaceable></term>
	<listitem>
	<para>
	The name (optionally schema-qualified) of a specific table or
	materialized view to vacuum. If the specified table is a partitioned
	table, all of its leaf partitions are vacuumed.
	</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><replaceable class="parameter">column_name</replaceable></term>
	<listitem>
	<para>
	The name of a specific column to analyze. Defaults to all columns.
	If a column list is specified, <literal>ANALYZE</literal> must also be
	specified.
	</para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>

	<refsect1>
	<title>Outputs</title>

	<para>
	When <literal>VERBOSE</literal> is specified, <command>VACUUM</command> emits
	progress messages to indicate which table is currently being
	processed. Various statistics about the tables are printed as well.
	</para>
	</refsect1>

	<refsect1>
	<title>Notes</title>

	<para>
	To vacuum a table, one must ordinarily be the table's owner or a
	superuser. However, database owners are allowed to
	vacuum all tables in their databases, except shared catalogs.
	(The restriction for shared catalogs means that a true database-wide
	<command>VACUUM</command> can only be performed by a superuser.)
	<command>VACUUM</command> will skip over any tables that the calling user
	does not have permission to vacuum.
	</para>

	<para>
	<command>VACUUM</command> cannot be executed inside a transaction block.
	</para>

	<para>
	For tables with <acronym>GIN</acronym> indexes, <command>VACUUM</command> (in
	any form) also completes any pending index insertions, by moving pending
	index entries to the appropriate places in the main <acronym>GIN</acronym> index
	structure. See <xref linkend="gin-fast-update"/> for details.
	</para>

	<para>
	We recommend that active production databases be
	vacuumed frequently (at least nightly), in order to
	remove dead rows. After adding or deleting a large number
	of rows, it might be a good idea to issue a <command>VACUUM
	ANALYZE</command> command for the affected table. This will update the
	system catalogs with
	the results of all recent changes, and allow the
	<productname>PostgreSQL</productname> query planner to make better
	choices in planning queries.
	</para>

	<para>
	The <option>FULL</option> option is not recommended for routine use,
	but might be useful in special cases. An example is when you have deleted
	or updated most of the rows in a table and would like the table to
	physically shrink to occupy less disk space and allow faster table
	scans. <command>VACUUM FULL</command> will usually shrink the table
	more than a plain <command>VACUUM</command> would.
	</para>

	<para>
	The <option>PARALLEL</option> option is used only for vacuum purposes.
	If this option is specified with the <option>ANALYZE</option> option,
	it does not affect <option>ANALYZE</option>.
	</para>

	<para>
	<command>VACUUM</command> causes a substantial increase in I/O traffic,
	which might cause poor performance for other active sessions. Therefore,
	it is sometimes advisable to use the cost-based vacuum delay feature. For
	parallel vacuum, each worker sleeps in proportion to the work done by that
	worker. See <xref linkend="runtime-config-resource-vacuum-cost"/> for
	details.
	</para>

	<para>
	<productname>PostgreSQL</productname> includes an <quote>autovacuum</quote>
	facility which can automate routine vacuum maintenance. For more
	information about automatic and manual vacuuming, see
	<xref linkend="routine-vacuuming"/>.
	</para>
	<para>
	Each backend running <command>VACUUM</command> without the
	<literal>FULL</literal> option will report its progress in the
	<structname>pg_stat_progress_vacuum</structname> view. Backends running
	<command>VACUUM FULL</command> will instead report their progress in the
	<structname>pg_stat_progress_cluster</structname> view. See
	<xref linkend="vacuum-progress-reporting"/> and
	<xref linkend="cluster-progress-reporting"/> for details.
	</para>
	</refsect1>

	<refsect1>
	<title>Examples</title>

	<para>
	To clean a single table <literal>onek</literal>, analyze it for
	the optimizer and print a detailed vacuum activity report:

	<programlisting>
	VACUUM (VERBOSE, ANALYZE) onek;
	</programlisting></para>
	</refsect1>

	<refsect1>
	<title>Compatibility</title>

	<para>
	There is no <command>VACUUM</command> statement in the SQL standard.
	</para>
	</refsect1>

	<refsect1>
	<title>See Also</title>

	<simplelist type="inline">
	<member><xref linkend="app-vacuumdb"/></member>
	<member><xref linkend="runtime-config-resource-vacuum-cost"/></member>
	<member><xref linkend="autovacuum"/></member>
	<member><xref linkend="vacuum-progress-reporting"/></member>
	<member><xref linkend="cluster-progress-reporting"/></member>
	</simplelist>
	</refsect1>
	</refentry>