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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!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 id="docContent" class="container-fluid col-10"><div 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 15.7 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-values.html" title="VALUES">Next</a></td></tr></table><hr /></div><div class="refentry" id="SQL-VACUUM"><div class="titlepage"></div><a id="id-1.9.3.184.1" 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 { AUTO | ON | OFF }
PROCESS_TOAST [ <em class="replaceable"><code>boolean</code></em> ]
TRUNCATE [ <em class="replaceable"><code>boolean</code></em> ]
PARALLEL <em class="replaceable"><code>integer</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-1.9.3.184.5"><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. It also allows us to leverage multiple CPUs in order to process
indexes. This feature is known as <em class="firstterm">parallel vacuum</em>.
To disable this feature, one can use <code class="literal">PARALLEL</code> option and
specify parallel workers as zero. <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 <code class="literal">ACCESS EXCLUSIVE</code> 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-1.9.3.184.6"><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="25.1.4. 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>
Normally, <code class="command">VACUUM</code> 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
<code class="command">VACUUM</code> to process indexes when there are more
than zero dead tuples. The default is <code class="literal">AUTO</code>,
which allows <code class="command">VACUUM</code> to skip index vacuuming
when appropriate. If <code class="literal">INDEX_CLEANUP</code> is set to
<code class="literal">ON</code>, <code class="command">VACUUM</code> will
conservatively remove all dead tuples from indexes. This may be
useful for backwards compatibility with earlier releases of
<span class="productname">PostgreSQL</span> where this was the
standard behavior.
</p><p>
<code class="literal">INDEX_CLEANUP</code> can also be set to
<code class="literal">OFF</code> to force <code class="command">VACUUM</code> to
<span class="emphasis"><em>always</em></span> skip index vacuuming, even when
there are many dead tuples in the table. This may be useful
when it is necessary to make <code class="command">VACUUM</code> run as
quickly as possible to avoid imminent transaction ID wraparound
(see <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="25.1.5. Preventing Transaction ID Wraparound Failures">Section 25.1.5</a>). However, the
wraparound failsafe mechanism controlled by <a class="xref" href="runtime-config-client.html#GUC-VACUUM-FAILSAFE-AGE">vacuum_failsafe_age</a> 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.
</p><p>
This option has no effect for tables that have no index and is
ignored if the <code class="literal">FULL</code> option is used. It also
has no effect on the transaction ID wraparound failsafe
mechanism. When triggered it will skip index vacuuming, even
when <code class="literal">INDEX_CLEANUP</code> is set to
<code class="literal">ON</code>.
</p></dd><dt><span class="term"><code class="literal">PROCESS_TOAST</code></span></dt><dd><p>
Specifies that <code class="command">VACUUM</code> should attempt to process the
corresponding <code class="literal">TOAST</code> 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
<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"><code class="literal">PARALLEL</code></span></dt><dd><p>
Perform index vacuum and index cleanup phases of <code class="command">VACUUM</code>
in parallel using <em class="replaceable"><code>integer</code></em>
background workers (for the details of each vacuum phase, please
refer to <a class="xref" href="progress-reporting.html#VACUUM-PHASES" title="Table 28.41. VACUUM Phases">Table 28.41</a>). 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 <code class="literal">PARALLEL</code> option if any which is
further limited by <a class="xref" href="runtime-config-resource.html#GUC-MAX-PARALLEL-MAINTENANCE-WORKERS">max_parallel_maintenance_workers</a>.
An index can participate in parallel vacuum if and only if the size of the
index is more than <a class="xref" href="runtime-config-query.html#GUC-MIN-PARALLEL-INDEX-SCAN-SIZE">min_parallel_index_scan_size</a>.
Please note that it is not guaranteed that the number of parallel workers
specified in <em class="replaceable"><code>integer</code></em> 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 <code class="literal">2</code> 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 <code class="literal">FULL</code> option.
</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>integer</code></em></span></dt><dd><p>
Specifies a non-negative integer value passed to the selected option.
</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-1.9.3.184.7"><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-1.9.3.184.8"><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="70.4.1. GIN Fast Update Technique">Section 70.4.1</a> for details.
</p><p>
We recommend that all databases be vacuumed regularly in
order to remove dead rows. <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="25.1. Routine Vacuuming">Section 25.1</a>.
</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>
The <code class="option">PARALLEL</code> option is used only for vacuum purposes.
If this option is specified with the <code class="option">ANALYZE</code> option,
it does not affect <code class="option">ANALYZE</code>.
</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. For
parallel vacuum, each worker sleeps in proportion to the work done by that
worker. See <a class="xref" href="runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-VACUUM-COST" title="20.4.4. Cost-based Vacuum Delay">Section 20.4.4</a> for
details.
</p><p>
Each backend running <code class="command">VACUUM</code> without the
<code class="literal">FULL</code> option will report its progress in the
<code class="structname">pg_stat_progress_vacuum</code> view. Backends running
<code class="command">VACUUM FULL</code> will instead report their progress in the
<code class="structname">pg_stat_progress_cluster</code> view. See
<a class="xref" href="progress-reporting.html#VACUUM-PROGRESS-REPORTING" title="28.4.3. VACUUM Progress Reporting">Section 28.4.3</a> and
<a class="xref" href="progress-reporting.html#CLUSTER-PROGRESS-REPORTING" title="28.4.4. CLUSTER Progress Reporting">Section 28.4.4</a> for details.
</p></div><div class="refsect1" id="id-1.9.3.184.9"><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-1.9.3.184.10"><h2>Compatibility</h2><p>
There is no <code class="command">VACUUM</code> statement in the SQL standard.
</p></div><div class="refsect1" id="id-1.9.3.184.11"><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="20.4.4. Cost-based Vacuum Delay">Section 20.4.4</a>, <a class="xref" href="routine-vacuuming.html#AUTOVACUUM" title="25.1.6. The Autovacuum Daemon">Section 25.1.6</a>, <a class="xref" href="progress-reporting.html#VACUUM-PROGRESS-REPORTING" title="28.4.3. VACUUM Progress Reporting">Section 28.4.3</a>, <a class="xref" href="progress-reporting.html#CLUSTER-PROGRESS-REPORTING" title="28.4.4. CLUSTER Progress Reporting">Section 28.4.4</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" title="UPDATE">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-values.html" title="VALUES">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" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> VALUES</td></tr></table></div></body></html>
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