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<title>REINDEX</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="sql-reindex"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>REINDEX — rebuild indexes</p>
</div>
<a name="id780050"></a><div class="refsynopsisdiv">
<h2>Synopsis</h2>
<pre class="synopsis">REINDEX { INDEX | TABLE | DATABASE | SYSTEM } <em class="replaceable"><code>name</code></em> [ FORCE ]</pre>
</div>
<div class="refsect1" lang="en">
<a name="id780074"></a><h2>Description</h2>
<p> <code class="command">REINDEX</code> rebuilds an index using the data
stored in the index's table, replacing the old copy of the index. There are
two main reasons to use <code class="command">REINDEX</code>:
</p>
<div class="itemizedlist"><ul type="disc">
<li><p> An index has become corrupted, and no longer contains valid
data. Although in theory this should never happen, in
practice indexes may become corrupted due to software bugs or
hardware failures. <code class="command">REINDEX</code> provides a
recovery method.
</p></li>
<li><p> The index in question contains a lot of dead index pages that
are not being reclaimed. This can occur with B-tree indexes in
<span class="productname">PostgreSQL</span> under certain access
patterns. <code class="command">REINDEX</code> provides a way to reduce
the space consumption of the index by writing a new version of
the index without the dead pages. See <a href="routine-reindex.html" title="22.2.Routine Reindexing">Section22.2, “Routine Reindexing”</a> for more information.
</p></li>
</ul></div>
<p>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id780142"></a><h2>Parameters</h2>
<div class="variablelist"><dl>
<dt><span class="term"><code class="literal">INDEX</code></span></dt>
<dd><p> Recreate the specified index.
</p></dd>
<dt><span class="term"><code class="literal">TABLE</code></span></dt>
<dd><p> Recreate all indexes of the specified table. If the table has a
secondary “<span class="quote">TOAST</span>” table, that is reindexed as well.
</p></dd>
<dt><span class="term"><code class="literal">DATABASE</code></span></dt>
<dd><p> Recreate all indexes within the current database.
Indexes on shared system catalogs are skipped except in stand-alone mode
(see below).
</p></dd>
<dt><span class="term"><code class="literal">SYSTEM</code></span></dt>
<dd><p> Recreate all indexes on system catalogs within the current database.
Indexes on user tables are not processed. Also, indexes on shared
system catalogs are skipped except in stand-alone mode (see below).
</p></dd>
<dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt>
<dd><p> The name of the specific index, table, or database to be
reindexed. Index and table names may be schema-qualified.
Presently, <code class="command">REINDEX DATABASE</code> and <code class="command">REINDEX SYSTEM</code>
can only reindex the current database, so their parameter must match
the current database's name.
</p></dd>
<dt><span class="term"><code class="literal">FORCE</code></span></dt>
<dd><p> This is an obsolete option; it is ignored if specified.
</p></dd>
</dl></div>
</div>
<div class="refsect1" lang="en">
<a name="id780247"></a><h2>Notes</h2>
<p> If you suspect corruption of an index on a user table, you can
simply rebuild that index, or all indexes on the table, using
<code class="command">REINDEX INDEX</code> or <code class="command">REINDEX TABLE</code>.
</p>
<p> Things are more difficult if you need to recover from corruption of
an index on a system table. In this case it's important for the
system to not have used any of the suspect indexes itself.
(Indeed, in this sort of scenario you may find that server
processes are crashing immediately at start-up, due to reliance on
the corrupted indexes.) To recover safely, the server must be started
with the <code class="option">-P</code> option, which prevents it from using
indexes for system catalog lookups.
</p>
<p> One way to do this is to shut down the postmaster and start a stand-alone
<span class="productname">PostgreSQL</span> server
with the <code class="option">-P</code> option included on its command line.
Then, <code class="command">REINDEX DATABASE</code>, <code class="command">REINDEX SYSTEM</code>,
<code class="command">REINDEX TABLE</code>, or <code class="command">REINDEX INDEX</code> can be
issued, depending on how much you want to reconstruct. If in
doubt, use <code class="command">REINDEX SYSTEM</code> to select
reconstruction of all system indexes in the database. Then quit
the standalone server session and restart the regular server.
See the <a href="app-postgres.html" title="postgres"><span class="refentrytitle"><a name="app-postgres-title"></a><span class="application">postgres</span></span></a> reference page for more
information about how to interact with the stand-alone server
interface.
</p>
<p> Alternatively, a regular server session can be started with
<code class="option">-P</code> included in its command line options.
The method for doing this varies across clients, but in all
<span class="application">libpq</span>-based clients, it is possible to set
the <code class="envar">PGOPTIONS</code> environment variable to <code class="literal">-P</code>
before starting the client. Note that while this method does not
require locking out other clients, it may still be wise to prevent
other users from connecting to the damaged database until repairs
have been completed.
</p>
<p> If corruption is suspected in the indexes of any of the shared
system catalogs (which are <code class="structname">pg_authid</code>,
<code class="structname">pg_auth_members</code>,
<code class="structname">pg_database</code>,
<code class="structname">pg_pltemplate</code>,
<code class="structname">pg_shdepend</code>, and
<code class="structname">pg_tablespace</code>), then a standalone server
must be used to repair it. <code class="command">REINDEX</code> will not process
shared catalogs in multiuser mode.
</p>
<p> For all indexes except the shared system catalogs, <code class="command">REINDEX</code>
is crash-safe and transaction-safe. <code class="command">REINDEX</code> is not
crash-safe for shared indexes, which is why this case is disallowed
during normal operation. If a failure occurs while reindexing one
of these catalogs in standalone mode, it will not be possible to
restart the regular server until the problem is rectified. (The
typical symptom of a partially rebuilt shared index is “<span class="quote">index is not
a btree</span>” errors.)
</p>
<p> <code class="command">REINDEX</code> is similar to a drop and recreate of the index
in that the index contents are rebuilt from scratch. However, the locking
considerations are rather different. <code class="command">REINDEX</code> locks out writes
but not reads of the index's parent table. It also takes an exclusive lock
on the specific index being processed, which will block reads that attempt
to use that index. In contrast, <code class="command">DROP INDEX</code> momentarily takes
exclusive lock on the parent table, blocking both writes and reads. The
subsequent <code class="command">CREATE INDEX</code> locks out writes but not reads; since
the index is not there, no read will attempt to use it, meaning that there
will be no blocking but reads may be forced into expensive sequential
scans. Another important point is that the drop/create approach
invalidates any cached query plans that use the index, while
<code class="command">REINDEX</code> does not.
</p>
<p> Reindexing a single index or table requires being the owner of that
index or table. Reindexing a database requires being the owner of
the database (note that the owner can therefore rebuild indexes of
tables owned by other users). Of course, superusers can always
reindex anything.
</p>
<p> Prior to <span class="productname">PostgreSQL</span> 8.1, <code class="command">REINDEX
DATABASE</code> processed only system indexes, not all indexes as one would
expect from the name. This has been changed to reduce the surprise
factor. The old behavior is available as <code class="command">REINDEX SYSTEM</code>.
</p>
<p> Prior to <span class="productname">PostgreSQL</span> 7.4, <code class="command">REINDEX
TABLE</code> did not automatically process TOAST tables, and so those had
to be reindexed by separate commands. This is still possible, but
redundant.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id780543"></a><h2>Examples</h2>
<p> Recreate the indexes on the table <code class="literal">my_table</code>:
</p>
<pre class="programlisting">REINDEX TABLE my_table;</pre>
<p>
</p>
<p> Rebuild a single index:
</p>
<pre class="programlisting">REINDEX INDEX my_index;</pre>
<p>
</p>
<p> Rebuild all indexes in a particular database, without trusting the
system indexes to be valid already:
</p>
<pre class="programlisting">$ <strong class="userinput"><code>export PGOPTIONS="-P"</code></strong>
$ <strong class="userinput"><code>psql broken_db</code></strong>
...
broken_db=> REINDEX DATABASE broken_db;
broken_db=> \q</pre>
<p>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id780599"></a><h2>Compatibility</h2>
<p> There is no <code class="command">REINDEX</code> command in the SQL standard.
</p>
</div>
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