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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>VACUUM</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="sql-update.html" title="UPDATE" /><link rel="next" href="sql-values.html" title="VALUES" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">VACUUM</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-update.html" title="UPDATE">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-values.html" title="VALUES">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-VACUUM"><div class="titlepage"></div><a id="id-1.9.3.183.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">VACUUM</span></h2><p>VACUUM — garbage-collect and optionally analyze a database</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
VACUUM [ ( <em class="replaceable"><code>option</code></em> [, ...] ) ] [ <em class="replaceable"><code>table_and_columns</code></em> [, ...] ]
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <em class="replaceable"><code>table_and_columns</code></em> [, ...] ]

<span class="phrase">where <em class="replaceable"><code>option</code></em> can be one of:</span>

    FULL [ <em class="replaceable"><code>boolean</code></em> ]
    FREEZE [ <em class="replaceable"><code>boolean</code></em> ]
    VERBOSE [ <em class="replaceable"><code>boolean</code></em> ]
    ANALYZE [ <em class="replaceable"><code>boolean</code></em> ]
    DISABLE_PAGE_SKIPPING [ <em class="replaceable"><code>boolean</code></em> ]
    SKIP_LOCKED [ <em class="replaceable"><code>boolean</code></em> ]
    INDEX_CLEANUP [ <em class="replaceable"><code>boolean</code></em> ]
    TRUNCATE [ <em class="replaceable"><code>boolean</code></em> ]

<span class="phrase">and <em class="replaceable"><code>table_and_columns</code></em> is:</span>

    <em class="replaceable"><code>table_name</code></em> [ ( <em class="replaceable"><code>column_name</code></em> [, ...] ) ]
</pre></div><div class="refsect1" id="id-1.9.3.183.5"><h2>Description</h2><p>
   <code class="command">VACUUM</code> reclaims storage occupied by dead tuples.
   In normal <span class="productname">PostgreSQL</span> operation, tuples that
   are deleted or obsoleted by an update are not physically removed from
   their table; they remain present until a <code class="command">VACUUM</code> is
   done.  Therefore it's necessary to do <code class="command">VACUUM</code>
   periodically, especially on frequently-updated tables.
  </p><p>
   Without a <em class="replaceable"><code>table_and_columns</code></em>
   list, <code class="command">VACUUM</code> processes every table and materialized view
   in the current database that the current user has permission to vacuum.
   With a list, <code class="command">VACUUM</code> processes only those table(s).
  </p><p>
   <code class="command">VACUUM ANALYZE</code> performs a <code class="command">VACUUM</code>
   and then an <code class="command">ANALYZE</code> for each selected table.  This
   is a handy combination form for routine maintenance scripts.  See
   <a class="xref" href="sql-analyze.html" title="ANALYZE"><span class="refentrytitle">ANALYZE</span></a>
   for more details about its processing.
  </p><p>
   Plain <code class="command">VACUUM</code> (without <code class="literal">FULL</code>) 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.  <code class="command">VACUUM FULL</code> 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 exclusive lock on each table while it is being processed.
  </p><p>
   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
   <span class="productname">PostgreSQL</span> 9.0;  the unparenthesized
   syntax is deprecated.
  </p></div><div class="refsect1" id="id-1.9.3.183.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">FULL</code></span></dt><dd><p>
      Selects <span class="quote">“<span class="quote">full</span>”</span> 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.
     </p></dd><dt><span class="term"><code class="literal">FREEZE</code></span></dt><dd><p>
      Selects aggressive <span class="quote">“<span class="quote">freezing</span>”</span> of tuples.
      Specifying <code class="literal">FREEZE</code> is equivalent to performing
      <code class="command">VACUUM</code> with the
      <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-MIN-AGE">vacuum_freeze_min_age</a> and
      <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-TABLE-AGE">vacuum_freeze_table_age</a> parameters
      set to zero.  Aggressive freezing is always performed when the
      table is rewritten, so this option is redundant when <code class="literal">FULL</code>
      is specified.
     </p></dd><dt><span class="term"><code class="literal">VERBOSE</code></span></dt><dd><p>
      Prints a detailed vacuum activity report for each table.
     </p></dd><dt><span class="term"><code class="literal">ANALYZE</code></span></dt><dd><p>
      Updates statistics used by the planner to determine the most
      efficient way to execute a query.
     </p></dd><dt><span class="term"><code class="literal">DISABLE_PAGE_SKIPPING</code></span></dt><dd><p>
      Normally, <code class="command">VACUUM</code> will skip pages based on the <a class="link" href="routine-vacuuming.html#VACUUM-FOR-VISIBILITY-MAP" title="24.1.4. Updating the Visibility Map">visibility map</a>.  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.
     </p></dd><dt><span class="term"><code class="literal">SKIP_LOCKED</code></span></dt><dd><p>
      Specifies that <code class="command">VACUUM</code> 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,
      <code class="command">VACUUM</code> may still block when opening the relation's
      indexes.  Additionally, <code class="command">VACUUM ANALYZE</code> may still
      block when acquiring sample rows from partitions, table inheritance
      children, and some types of foreign tables.  Also, while
      <code class="command">VACUUM</code> ordinarily processes all partitions of
      specified partitioned tables, this option will cause
      <code class="command">VACUUM</code> to skip all partitions if there is a
      conflicting lock on the partitioned table.
     </p></dd><dt><span class="term"><code class="literal">INDEX_CLEANUP</code></span></dt><dd><p>
      Specifies that <code class="command">VACUUM</code> should attempt to remove
      index entries pointing to dead tuples.  This is normally the desired
      behavior and is the default unless the
      <code class="literal">vacuum_index_cleanup</code> option has been set to false
      for the table to be vacuumed.  Setting this option to false may be
      useful when it is necessary to make vacuum run as quickly as possible,
      for example to avoid imminent transaction ID wraparound
      (see <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="24.1.5. Preventing Transaction ID Wraparound Failures">Section 24.1.5</a>).  However, 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.  This option has no effect
      for tables that do not have an index and is ignored if the
      <code class="literal">FULL</code> option is used.
     </p></dd><dt><span class="term"><code class="literal">TRUNCATE</code></span></dt><dd><p>
      Specifies that <code class="command">VACUUM</code> 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 <code class="literal">vacuum_truncate</code>
      option has been set to false for the table to be vacuumed.
      Setting this option to false may be useful to avoid
      <code class="literal">ACCESS EXCLUSIVE</code> lock on the table that
      the truncation requires. This option is ignored if the
      <code class="literal">FULL</code> option is used.
     </p></dd><dt><span class="term"><em class="replaceable"><code>boolean</code></em></span></dt><dd><p>
      Specifies whether the selected option should be turned on or off.
      You can write <code class="literal">TRUE</code>, <code class="literal">ON</code>, or
      <code class="literal">1</code> to enable the option, and <code class="literal">FALSE</code>,
      <code class="literal">OFF</code>, or <code class="literal">0</code> to disable it.  The
      <em class="replaceable"><code>boolean</code></em> value can also
      be omitted, in which case <code class="literal">TRUE</code> is assumed.
     </p></dd><dt><span class="term"><em class="replaceable"><code>table_name</code></em></span></dt><dd><p>
      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.
     </p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>
      The name of a specific column to analyze. Defaults to all columns.
      If a column list is specified, <code class="literal">ANALYZE</code> must also be
      specified.
     </p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.183.7"><h2>Outputs</h2><p>
    When <code class="literal">VERBOSE</code> is specified, <code class="command">VACUUM</code> emits
    progress messages to indicate which table is currently being
    processed.  Various statistics about the tables are printed as well.
   </p></div><div class="refsect1" id="id-1.9.3.183.8"><h2>Notes</h2><p>
    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
    <code class="command">VACUUM</code> can only be performed by a superuser.)
    <code class="command">VACUUM</code> will skip over any tables that the calling user
    does not have permission to vacuum.
   </p><p>
    <code class="command">VACUUM</code> cannot be executed inside a transaction block.
   </p><p>
    For tables with <acronym class="acronym">GIN</acronym> indexes, <code class="command">VACUUM</code> (in
    any form) also completes any pending index insertions, by moving pending
    index entries to the appropriate places in the main <acronym class="acronym">GIN</acronym> index
    structure.  See <a class="xref" href="gin-implementation.html#GIN-FAST-UPDATE" title="66.4.1. GIN Fast Update Technique">Section 66.4.1</a> for details.
   </p><p>
    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 <code class="command">VACUUM
    ANALYZE</code> command for the affected table. This will update the
    system catalogs with
    the results of all recent changes, and allow the
    <span class="productname">PostgreSQL</span> query planner to make better
    choices in planning queries.
   </p><p>
    The <code class="option">FULL</code> 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. <code class="command">VACUUM FULL</code> will usually shrink the table
    more than a plain <code class="command">VACUUM</code> would.
   </p><p>
    <code class="command">VACUUM</code> 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.
    See <a class="xref" href="runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-VACUUM-COST" title="19.4.4. Cost-based Vacuum Delay">Section 19.4.4</a> for details.
   </p><p>
    <span class="productname">PostgreSQL</span> includes an <span class="quote">“<span class="quote">autovacuum</span>”</span>
    facility which can automate routine vacuum maintenance.  For more
    information about automatic and manual vacuuming, see
    <a class="xref" href="routine-vacuuming.html" title="24.1. Routine Vacuuming">Section 24.1</a>.
   </p></div><div class="refsect1" id="id-1.9.3.183.9"><h2>Examples</h2><p>
   To clean a single table <code class="literal">onek</code>, analyze it for
   the optimizer and print a detailed vacuum activity report:

</p><pre class="programlisting">
VACUUM (VERBOSE, ANALYZE) onek;
</pre></div><div class="refsect1" id="id-1.9.3.183.10"><h2>Compatibility</h2><p>
   There is no <code class="command">VACUUM</code> statement in the SQL standard.
  </p></div><div class="refsect1" id="id-1.9.3.183.11"><h2>See Also</h2><span class="simplelist"><a class="xref" href="app-vacuumdb.html" title="vacuumdb"><span class="refentrytitle"><span class="application">vacuumdb</span></span></a>, <a class="xref" href="runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-VACUUM-COST" title="19.4.4. Cost-based Vacuum Delay">Section 19.4.4</a>, <a class="xref" href="routine-vacuuming.html#AUTOVACUUM" title="24.1.6. The Autovacuum Daemon">Section 24.1.6</a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-update.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-values.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">UPDATE </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> VALUES</td></tr></table></div></body></html>