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Clarify vacuum lazy can shrink a file under certain circumstances.

This commit is contained in:
Bruce Momjian 2005-12-07 05:35:53 +00:00
parent 887a7c61f6
commit 95aca45010
1 changed files with 7 additions and 6 deletions
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13
doc/src/sgml/maintenance.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.51 2005/11/04 23:14:00 petere Exp $
$PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.52 2005/12/07 05:35:53 momjian Exp $
-->
<chapter id="maintenance">
@ -141,11 +141,12 @@ $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.51 2005/11/04 23:14:00 pete
command. The first form, known as <quote>lazy vacuum</quote> or
just <command>VACUUM</command>, marks expired data in tables and
indexes for future reuse; it does <emphasis>not</emphasis> attempt
to reclaim the space used by this expired data
immediately. Therefore, the table file is not shortened, and any
unused space in the file is not returned to the operating
system. This variant of <command>VACUUM</command> can be run
concurrently with normal database operations.
to reclaim the space used by this expired data unless the space is
at the end of the table and an exclusive lock can be obtained easily
on the table. Unused space at the start or middle of the file does
not result in the file being shortened and space returned to the
operating system. This variant of <command>VACUUM</command> can be
run concurrently with normal database operations.
</para>
<para>