Baoding-FenShuaJiang
/
Green_GoodERP18_FSJ_Standard


			
				
					
						
						
							
							<?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>REINDEX</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-refreshmaterializedview.html" title="REFRESH MATERIALIZED VIEW" /><link rel="next" href="sql-release-savepoint.html" title="RELEASE SAVEPOINT" /></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">REINDEX</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-refreshmaterializedview.html" title="REFRESH MATERIALIZED VIEW">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-release-savepoint.html" title="RELEASE SAVEPOINT">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-REINDEX"><div class="titlepage"></div><a id="id-1.9.3.162.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">REINDEX</span></h2><p>REINDEX — rebuild indexes</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
REINDEX [ ( VERBOSE ) ] { INDEX | TABLE | SCHEMA | DATABASE | SYSTEM } [ CONCURRENTLY ] <em class="replaceable"><code>name</code></em>
</pre></div><div class="refsect1" id="id-1.9.3.162.5"><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
   several scenarios in which to use <code class="command">REINDEX</code>:

   </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
      An index has become corrupted, and no longer contains valid
      data. Although in theory this should never happen, in
      practice indexes can become corrupted due to software bugs or
      hardware failures.  <code class="command">REINDEX</code> provides a
      recovery method.
     </p></li><li class="listitem"><p>
      An index has become <span class="quote">“<span class="quote">bloated</span>”</span>, that is it contains many
      empty or nearly-empty pages.  This can occur with B-tree indexes in
      <span class="productname">PostgreSQL</span> under certain uncommon 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 class="xref" href="routine-reindex.html" title="24.2. Routine Reindexing">Section 24.2</a> for more information.
     </p></li><li class="listitem"><p>
      You have altered a storage parameter (such as fillfactor)
      for an index, and wish to ensure that the change has taken full effect.
     </p></li><li class="listitem"><p>
      If an index build fails with the <code class="literal">CONCURRENTLY</code> option,
      this index is left as <span class="quote">“<span class="quote">invalid</span>”</span>. Such indexes are useless
      but it can be convenient to use <code class="command">REINDEX</code> to rebuild
      them. Note that only <code class="command">REINDEX INDEX</code> is able
      to perform a concurrent build on an invalid index.
     </p></li></ul></div></div><div class="refsect1" id="id-1.9.3.162.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><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">“<span class="quote">TOAST</span>”</span> table, that is reindexed as well.
     </p></dd><dt><span class="term"><code class="literal">SCHEMA</code></span></dt><dd><p>
      Recreate all indexes of the specified schema.  If a table of this
      schema has a secondary <span class="quote">“<span class="quote">TOAST</span>”</span> table, that is reindexed as
      well. Indexes on shared system catalogs are also processed.
      This form of <code class="command">REINDEX</code> cannot be executed inside a
      transaction block.
     </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 also processed.
      This form of <code class="command">REINDEX</code> cannot be executed inside a
      transaction block.
     </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 shared system catalogs are included.
      Indexes on user tables are not processed.
      This form of <code class="command">REINDEX</code> cannot be executed inside a
      transaction block.
     </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 can 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">CONCURRENTLY</code></span></dt><dd><p>
      When this option is used, <span class="productname">PostgreSQL</span> will rebuild the
      index without taking any locks that prevent concurrent inserts,
      updates, or deletes on the table; whereas a standard index rebuild
      locks out writes (but not reads) on the table until it's done.
      There are several caveats to be aware of when using this option
      — see <a class="xref" href="sql-reindex.html#SQL-REINDEX-CONCURRENTLY" title="Rebuilding Indexes Concurrently">Rebuilding Indexes Concurrently</a>.
     </p><p>
      For temporary tables, <code class="command">REINDEX</code> is always
      non-concurrent, as no other session can access them, and
      non-concurrent reindex is cheaper.
     </p></dd><dt><span class="term"><code class="literal">VERBOSE</code></span></dt><dd><p>
      Prints a progress report as each index is reindexed.
     </p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.162.7"><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 might 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 server and start a single-user
   <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 single-user server session and restart the regular server.
   See the <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a> reference page for more
   information about how to interact with the single-user 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 might still be wise to prevent
   other users from connecting to the damaged database until repairs
   have been completed.
  </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
   an 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 might be forced into expensive sequential
   scans.
  </p><p>
   Reindexing a single index or table requires being the owner of that
   index or table.  Reindexing a schema or database requires being the
   owner of that schema or database.  Note that is therefore sometimes
   possible for non-superusers to rebuild indexes of tables owned by
   other users.  However, as a special exception, when
   <code class="command">REINDEX DATABASE</code>, <code class="command">REINDEX SCHEMA</code>
   or <code class="command">REINDEX SYSTEM</code> is issued by a non-superuser,
   indexes on shared catalogs will be skipped unless the user owns the
   catalog (which typically won't be the case).  Of course, superusers
   can always reindex anything.
  </p><p>
   Reindexing partitioned tables or partitioned indexes is not supported.
   Each individual partition can be reindexed separately instead.
  </p><div class="refsect2" id="SQL-REINDEX-CONCURRENTLY"><h3>Rebuilding Indexes Concurrently</h3><a id="id-1.9.3.162.7.9.2" class="indexterm"></a><p>
    Rebuilding an index can interfere with regular operation of a database.
    Normally <span class="productname">PostgreSQL</span> locks the table whose index is rebuilt
    against writes and performs the entire index build with a single scan of the
    table. Other transactions can still read the table, but if they try to
    insert, update, or delete rows in the table they will block until the
    index rebuild is finished. This could have a severe effect if the system is
    a live production database. Very large tables can take many hours to be
    indexed, and even for smaller tables, an index rebuild can lock out writers
    for periods that are unacceptably long for a production system.
   </p><p>
    <span class="productname">PostgreSQL</span> supports rebuilding indexes with minimum locking
    of writes.  This method is invoked by specifying the
    <code class="literal">CONCURRENTLY</code> option of <code class="command">REINDEX</code>. When this option
    is used, <span class="productname">PostgreSQL</span> must perform two scans of the table
    for each index that needs to be rebuilt and wait for termination of
    all existing transactions that could potentially use the index.
    This method requires more total work than a standard index
    rebuild and takes significantly longer to complete as it needs to wait
    for unfinished transactions that might modify the index. However, since
    it allows normal operations to continue while the index is being rebuilt, this
    method is useful for rebuilding indexes in a production environment. Of
    course, the extra CPU, memory and I/O load imposed by the index rebuild
    may slow down other operations.
   </p><p>
    The following steps occur in a concurrent reindex.  Each step is run in a
    separate transaction.  If there are multiple indexes to be rebuilt, then
    each step loops through all the indexes before moving to the next step.

    </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
       A new temporary index definition is added to the catalog
       <code class="literal">pg_index</code>.  This definition will be used to replace
       the old index.  A <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock at
       session level is taken on the indexes being reindexed as well as their
       associated tables to prevent any schema modification while processing.
      </p></li><li class="listitem"><p>
       A first pass to build the index is done for each new index.  Once the
       index is built, its flag <code class="literal">pg_index.indisready</code> is
       switched to <span class="quote">“<span class="quote">true</span>”</span> to make it ready for inserts, making it
       visible to other sessions once the transaction that performed the build
       is finished.  This step is done in a separate transaction for each
       index.
      </p></li><li class="listitem"><p>
       Then a second pass is performed to add tuples that were added while the
       first pass was running.  This step is also done in a separate
       transaction for each index.
      </p></li><li class="listitem"><p>
       All the constraints that refer to the index are changed to refer to the
       new index definition, and the names of the indexes are changed.  At
       this point, <code class="literal">pg_index.indisvalid</code> is switched to
       <span class="quote">“<span class="quote">true</span>”</span> for the new index and to <span class="quote">“<span class="quote">false</span>”</span> for
       the old, and a cache invalidation is done causing all sessions that
       referenced the old index to be invalidated.
      </p></li><li class="listitem"><p>
       The old indexes have <code class="literal">pg_index.indisready</code> switched to
       <span class="quote">“<span class="quote">false</span>”</span> to prevent any new tuple insertions, after waiting
       for running queries that might reference the old index to complete.
      </p></li><li class="listitem"><p>
       The old indexes are dropped.  The <code class="literal">SHARE UPDATE
       EXCLUSIVE</code> session locks for the indexes and the table are
       released.
      </p></li></ol></div><p>
   </p><p>
    If a problem arises while rebuilding the indexes, such as a
    uniqueness violation in a unique index, the <code class="command">REINDEX</code>
    command will fail but leave behind an <span class="quote">“<span class="quote">invalid</span>”</span> new index in addition to
    the pre-existing one. This index will be ignored for querying purposes
    because it might be incomplete; however it will still consume update
    overhead. The <span class="application">psql</span> <code class="command">\d</code> command will report
    such an index as <code class="literal">INVALID</code>:

</p><pre class="programlisting">
postgres=# \d tab
       Table "public.tab"
 Column |  Type   | Modifiers
--------+---------+-----------
 col    | integer |
Indexes:
    "idx" btree (col)
    "idx_ccnew" btree (col) INVALID
</pre><p>

    The recommended recovery method in such cases is to drop the invalid index
    and try again to perform <code class="command">REINDEX CONCURRENTLY</code>.  The
    concurrent index created during the processing has a name ending in the
    suffix <code class="literal">ccnew</code>, or <code class="literal">ccold</code> if it is an
    old index definition which we failed to drop. Invalid indexes can be
    dropped using <code class="literal">DROP INDEX</code>, including invalid toast
    indexes.
   </p><p>
    Regular index builds permit other regular index builds on the same table
    to occur simultaneously, but only one concurrent index build can occur on a
    table at a time. In both cases, no other types of schema modification on
    the table are allowed meanwhile.  Another difference is that a regular
    <code class="command">REINDEX TABLE</code> or <code class="command">REINDEX INDEX</code>
    command can be performed within a transaction block, but <code class="command">REINDEX
    CONCURRENTLY</code> cannot.
   </p><p>
    <code class="command">REINDEX SYSTEM</code> does not support
    <code class="command">CONCURRENTLY</code> since system catalogs cannot be reindexed
    concurrently.
   </p><p>
    Furthermore, indexes for exclusion constraints cannot be reindexed
    concurrently.  If such an index is named directly in this command, an
    error is raised.  If a table or database with exclusion constraint indexes
    is reindexed concurrently, those indexes will be skipped.  (It is possible
    to reindex such indexes without the <code class="command">CONCURRENTLY</code> option.)
   </p></div></div><div class="refsect1" id="id-1.9.3.162.8"><h2>Examples</h2><p>
   Rebuild a single index:

</p><pre class="programlisting">
REINDEX INDEX my_index;
</pre><p>
  </p><p>
   Rebuild all the indexes on the table <code class="literal">my_table</code>:

</p><pre class="programlisting">
REINDEX TABLE my_table;
</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=&gt; REINDEX DATABASE broken_db;
broken_db=&gt; \q
</pre><p>
   Rebuild indexes for a table, without blocking read and write operations
   on involved relations while reindexing is in progress:

</p><pre class="programlisting">
REINDEX TABLE CONCURRENTLY my_broken_table;
</pre></div><div class="refsect1" id="id-1.9.3.162.9"><h2>Compatibility</h2><p>
   There is no <code class="command">REINDEX</code> command in the SQL standard.
  </p></div><div class="refsect1" id="id-1.9.3.162.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a>, <a class="xref" href="sql-dropindex.html" title="DROP INDEX"><span class="refentrytitle">DROP INDEX</span></a>, <a class="xref" href="app-reindexdb.html" title="reindexdb"><span class="refentrytitle"><span class="application">reindexdb</span></span></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-refreshmaterializedview.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-release-savepoint.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">REFRESH MATERIALIZED VIEW </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> RELEASE SAVEPOINT</td></tr></table></div></body></html>