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Update documentation mention of VACUUM FULL and CLUSTER where

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appropriate.

Guillaume Cottenceau
This commit is contained in:
Bruce Momjian 2007-05-30 19:45:01 +00:00
parent f14f27dd38
commit 9e38d2a4a8
2 changed files with 15 additions and 9 deletions
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13
doc/src/sgml/maintenance.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.74 2007/05/15 15:52:40 neilc Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.75 2007/05/30 19:45:00 momjian Exp $ -->
<chapter id="maintenance">
<title>Routine Database Maintenance Tasks</title>
@ -157,7 +157,8 @@
command. This uses a more aggressive algorithm for reclaiming the
space consumed by dead row versions. Any space that is freed by
<command>VACUUM FULL</command> is immediately returned to the
operating system. Unfortunately, this variant of the
operating system, and the table data is physically compacted on
the disk. Unfortunately, this variant of the
<command>VACUUM</command> command acquires an exclusive lock on
each table while <command>VACUUM FULL</command> is processing
it. Therefore, frequently using <command>VACUUM FULL</command> can
@ -168,12 +169,16 @@
<para>
The standard form of <command>VACUUM</> is best used with the goal
of maintaining a fairly level steady-state usage of disk space. If
you need to return disk space to the operating system you can use
you need to return disk space to the operating system, you can use
<command>VACUUM FULL</> &mdash; but what's the point of releasing disk
space that will only have to be allocated again soon? Moderately
frequent standard <command>VACUUM</> runs are a better approach
than infrequent <command>VACUUM FULL</> runs for maintaining
heavily-updated tables.
heavily-updated tables. However, if some heavily-updated tables
have gone too long with infrequent <command>VACUUM</>, you can
use <command>VACUUM FULL</> or <command>CLUSTER</> to get performance
back (it is much slower to scan a table containing almost only dead
rows).
</para>
<para>

11
doc/src/sgml/ref/vacuum.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.47 2007/01/31 23:26:04 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.48 2007/05/30 19:45:01 momjian Exp $
PostgreSQL documentation
-->
@ -164,10 +164,11 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">
<para>
The <option>FULL</option> option is not recommended for routine use,
but might be useful in special cases. An example is when you have deleted
most of the rows in a table and would like the table to physically shrink
to occupy less disk space. <command>VACUUM FULL</command> will usually
shrink the table more than a plain <command>VACUUM</command> would.
The <option>FULL</option> option does not shrink indexes; a periodic
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. <command>VACUUM FULL</command> will usually shrink the table
more than a plain <command>VACUUM</command> would. The
<option>FULL</option> option does not shrink indexes; a periodic
<command>REINDEX</> is still recommended. In fact, it is often faster
to drop all indexes, <command>VACUUM FULL</>, and recreate the indexes.
</para>