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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 Vsnapshot" /><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 11.5 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
FREEZE
VERBOSE
ANALYZE
DISABLE_PAGE_SKIPPING
<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"><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>
