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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!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">

  3. VACUUM [ ( <em class="replaceable"><code>option</code></em> [, ...] ) ] [ <em class="replaceable"><code>table_and_columns</code></em> [, ...] ]

  4. VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <em class="replaceable"><code>table_and_columns</code></em> [, ...] ]

  5. 

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

  7. 

  8.     FULL [ <em class="replaceable"><code>boolean</code></em> ]

  9.     FREEZE [ <em class="replaceable"><code>boolean</code></em> ]

  10.     VERBOSE [ <em class="replaceable"><code>boolean</code></em> ]

  11.     ANALYZE [ <em class="replaceable"><code>boolean</code></em> ]

  12.     DISABLE_PAGE_SKIPPING [ <em class="replaceable"><code>boolean</code></em> ]

  13.     SKIP_LOCKED [ <em class="replaceable"><code>boolean</code></em> ]

  14.     INDEX_CLEANUP [ <em class="replaceable"><code>boolean</code></em> ]

  15.     TRUNCATE [ <em class="replaceable"><code>boolean</code></em> ]

  16. 

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

  18. 

  19.     <em class="replaceable"><code>table_name</code></em> [ ( <em class="replaceable"><code>column_name</code></em> [, ...] ) ]

  20. </pre></div><div class="refsect1" id="id-1.9.3.183.5"><h2>Description</h2><p>

  21.    <code class="command">VACUUM</code> reclaims storage occupied by dead tuples.

  22.    In normal <span class="productname">PostgreSQL</span> operation, tuples that

  23.    are deleted or obsoleted by an update are not physically removed from

  24.    their table; they remain present until a <code class="command">VACUUM</code> is

  25.    done.  Therefore it's necessary to do <code class="command">VACUUM</code>

  26.    periodically, especially on frequently-updated tables.

  27.   </p><p>

  28.    Without a <em class="replaceable"><code>table_and_columns</code></em>

  29.    list, <code class="command">VACUUM</code> processes every table and materialized view

  30.    in the current database that the current user has permission to vacuum.

  31.    With a list, <code class="command">VACUUM</code> processes only those table(s).

  32.   </p><p>

  33.    <code class="command">VACUUM ANALYZE</code> performs a <code class="command">VACUUM</code>

  34.    and then an <code class="command">ANALYZE</code> for each selected table.  This

  35.    is a handy combination form for routine maintenance scripts.  See

  36.    <a class="xref" href="sql-analyze.html" title="ANALYZE"><span class="refentrytitle">ANALYZE</span></a>

  37.    for more details about its processing.

  38.   </p><p>

  39.    Plain <code class="command">VACUUM</code> (without <code class="literal">FULL</code>) simply reclaims

  40.    space and makes it

  41.    available for re-use.  This form of the command can operate in parallel

  42.    with normal reading and writing of the table, as an exclusive lock

  43.    is not obtained.  However, extra space is not returned to the operating

  44.    system (in most cases); it's just kept available for re-use within the

  45.    same table.  <code class="command">VACUUM FULL</code> rewrites the entire contents

  46.    of the table into a new disk file with no extra space, allowing unused

  47.    space to be returned to the operating system.  This form is much slower and

  48.    requires an exclusive lock on each table while it is being processed.

  49.   </p><p>

  50.    When the option list is surrounded by parentheses, the options can be

  51.    written in any order.  Without parentheses, options must be specified

  52.    in exactly the order shown above.

  53.    The parenthesized syntax was added in

  54.    <span class="productname">PostgreSQL</span> 9.0;  the unparenthesized

  55.    syntax is deprecated.

  56.   </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>

  57.       Selects <span class="quote">“<span class="quote">full</span>”</span> vacuum, which can reclaim more

  58.       space, but takes much longer and exclusively locks the table.

  59.       This method also requires extra disk space, since it writes a

  60.       new copy of the table and doesn't release the old copy until

  61.       the operation is complete.  Usually this should only be used when a

  62.       significant amount of space needs to be reclaimed from within the table.

  63.      </p></dd><dt><span class="term"><code class="literal">FREEZE</code></span></dt><dd><p>

  64.       Selects aggressive <span class="quote">“<span class="quote">freezing</span>”</span> of tuples.

  65.       Specifying <code class="literal">FREEZE</code> is equivalent to performing

  66.       <code class="command">VACUUM</code> with the

  67.       <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-MIN-AGE">vacuum_freeze_min_age</a> and

  68.       <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FREEZE-TABLE-AGE">vacuum_freeze_table_age</a> parameters

  69.       set to zero.  Aggressive freezing is always performed when the

  70.       table is rewritten, so this option is redundant when <code class="literal">FULL</code>

  71.       is specified.

  72.      </p></dd><dt><span class="term"><code class="literal">VERBOSE</code></span></dt><dd><p>

  73.       Prints a detailed vacuum activity report for each table.

  74.      </p></dd><dt><span class="term"><code class="literal">ANALYZE</code></span></dt><dd><p>

  75.       Updates statistics used by the planner to determine the most

  76.       efficient way to execute a query.

  77.      </p></dd><dt><span class="term"><code class="literal">DISABLE_PAGE_SKIPPING</code></span></dt><dd><p>

  78.       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

  79.       all tuples are known to be frozen can always be skipped, and those

  80.       where all tuples are known to be visible to all transactions may be

  81.       skipped except when performing an aggressive vacuum.  Furthermore,

  82.       except when performing an aggressive vacuum, some pages may be skipped

  83.       in order to avoid waiting for other sessions to finish using them.

  84.       This option disables all page-skipping behavior, and is intended to

  85.       be used only when the contents of the visibility map are

  86.       suspect, which should happen only if there is a hardware or software

  87.       issue causing database corruption.

  88.      </p></dd><dt><span class="term"><code class="literal">SKIP_LOCKED</code></span></dt><dd><p>

  89.       Specifies that <code class="command">VACUUM</code> should not wait for any

  90.       conflicting locks to be released when beginning work on a relation:

  91.       if a relation cannot be locked immediately without waiting, the relation

  92.       is skipped.  Note that even with this option,

  93.       <code class="command">VACUUM</code> may still block when opening the relation's

  94.       indexes.  Additionally, <code class="command">VACUUM ANALYZE</code> may still

  95.       block when acquiring sample rows from partitions, table inheritance

  96.       children, and some types of foreign tables.  Also, while

  97.       <code class="command">VACUUM</code> ordinarily processes all partitions of

  98.       specified partitioned tables, this option will cause

  99.       <code class="command">VACUUM</code> to skip all partitions if there is a

  100.       conflicting lock on the partitioned table.

  101.      </p></dd><dt><span class="term"><code class="literal">INDEX_CLEANUP</code></span></dt><dd><p>

  102.       Specifies that <code class="command">VACUUM</code> should attempt to remove

  103.       index entries pointing to dead tuples.  This is normally the desired

  104.       behavior and is the default unless the

  105.       <code class="literal">vacuum_index_cleanup</code> option has been set to false

  106.       for the table to be vacuumed.  Setting this option to false may be

  107.       useful when it is necessary to make vacuum run as quickly as possible,

  108.       for example to avoid imminent transaction ID wraparound

  109.       (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

  110.       cleanup is not performed regularly, performance may suffer, because

  111.       as the table is modified, indexes will accumulate dead tuples

  112.       and the table itself will accumulate dead line pointers that cannot be

  113.       removed until index cleanup is completed.  This option has no effect

  114.       for tables that do not have an index and is ignored if the

  115.       <code class="literal">FULL</code> option is used.

  116.      </p></dd><dt><span class="term"><code class="literal">TRUNCATE</code></span></dt><dd><p>

  117.       Specifies that <code class="command">VACUUM</code> should attempt to

  118.       truncate off any empty pages at the end of the table and allow

  119.       the disk space for the truncated pages to be returned to

  120.       the operating system. This is normally the desired behavior

  121.       and is the default unless the <code class="literal">vacuum_truncate</code>

  122.       option has been set to false for the table to be vacuumed.

  123.       Setting this option to false may be useful to avoid

  124.       <code class="literal">ACCESS EXCLUSIVE</code> lock on the table that

  125.       the truncation requires. This option is ignored if the

  126.       <code class="literal">FULL</code> option is used.

  127.      </p></dd><dt><span class="term"><em class="replaceable"><code>boolean</code></em></span></dt><dd><p>

  128.       Specifies whether the selected option should be turned on or off.

  129.       You can write <code class="literal">TRUE</code>, <code class="literal">ON</code>, or

  130.       <code class="literal">1</code> to enable the option, and <code class="literal">FALSE</code>,

  131.       <code class="literal">OFF</code>, or <code class="literal">0</code> to disable it.  The

  132.       <em class="replaceable"><code>boolean</code></em> value can also

  133.       be omitted, in which case <code class="literal">TRUE</code> is assumed.

  134.      </p></dd><dt><span class="term"><em class="replaceable"><code>table_name</code></em></span></dt><dd><p>

  135.       The name (optionally schema-qualified) of a specific table or

  136.       materialized view to vacuum.  If the specified table is a partitioned

  137.       table, all of its leaf partitions are vacuumed.

  138.      </p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>

  139.       The name of a specific column to analyze. Defaults to all columns.

  140.       If a column list is specified, <code class="literal">ANALYZE</code> must also be

  141.       specified.

  142.      </p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.183.7"><h2>Outputs</h2><p>

  143.     When <code class="literal">VERBOSE</code> is specified, <code class="command">VACUUM</code> emits

  144.     progress messages to indicate which table is currently being

  145.     processed.  Various statistics about the tables are printed as well.

  146.    </p></div><div class="refsect1" id="id-1.9.3.183.8"><h2>Notes</h2><p>

  147.     To vacuum a table, one must ordinarily be the table's owner or a

  148.     superuser.  However, database owners are allowed to

  149.     vacuum all tables in their databases, except shared catalogs.

  150.     (The restriction for shared catalogs means that a true database-wide

  151.     <code class="command">VACUUM</code> can only be performed by a superuser.)

  152.     <code class="command">VACUUM</code> will skip over any tables that the calling user

  153.     does not have permission to vacuum.

  154.    </p><p>

  155.     <code class="command">VACUUM</code> cannot be executed inside a transaction block.

  156.    </p><p>

  157.     For tables with <acronym class="acronym">GIN</acronym> indexes, <code class="command">VACUUM</code> (in

  158.     any form) also completes any pending index insertions, by moving pending

  159.     index entries to the appropriate places in the main <acronym class="acronym">GIN</acronym> index

  160.     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.

  161.    </p><p>

  162.     We recommend that active production databases be

  163.     vacuumed frequently (at least nightly), in order to

  164.     remove dead rows. After adding or deleting a large number

  165.     of rows, it might be a good idea to issue a <code class="command">VACUUM

  166.     ANALYZE</code> command for the affected table. This will update the

  167.     system catalogs with

  168.     the results of all recent changes, and allow the

  169.     <span class="productname">PostgreSQL</span> query planner to make better

  170.     choices in planning queries.

  171.    </p><p>

  172.     The <code class="option">FULL</code> option is not recommended for routine use,

  173.     but might be useful in special cases.  An example is when you have deleted

  174.     or updated most of the rows in a table and would like the table to

  175.     physically shrink to occupy less disk space and allow faster table

  176.     scans. <code class="command">VACUUM FULL</code> will usually shrink the table

  177.     more than a plain <code class="command">VACUUM</code> would.

  178.    </p><p>

  179.     <code class="command">VACUUM</code> causes a substantial increase in I/O traffic,

  180.     which might cause poor performance for other active sessions.  Therefore,

  181.     it is sometimes advisable to use the cost-based vacuum delay feature.

  182.     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.

  183.    </p><p>

  184.     <span class="productname">PostgreSQL</span> includes an <span class="quote">“<span class="quote">autovacuum</span>”</span>

  185.     facility which can automate routine vacuum maintenance.  For more

  186.     information about automatic and manual vacuuming, see

  187.     <a class="xref" href="routine-vacuuming.html" title="24.1. Routine Vacuuming">Section 24.1</a>.

  188.    </p></div><div class="refsect1" id="id-1.9.3.183.9"><h2>Examples</h2><p>

  189.    To clean a single table <code class="literal">onek</code>, analyze it for

  190.    the optimizer and print a detailed vacuum activity report:

  191. 

  192. </p><pre class="programlisting">

  193. VACUUM (VERBOSE, ANALYZE) onek;

  194. </pre></div><div class="refsect1" id="id-1.9.3.183.10"><h2>Compatibility</h2><p>

  195.    There is no <code class="command">VACUUM</code> statement in the SQL standard.

  196.   </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>
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