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Clarify vacuum lazy can shrink a file under certain circumstances.

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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"> <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 command. The first form, known as <quote>lazy vacuum</quote> or
just <command>VACUUM</command>, marks expired data in tables and just <command>VACUUM</command>, marks expired data in tables and
indexes for future reuse; it does <emphasis>not</emphasis> attempt indexes for future reuse; it does <emphasis>not</emphasis> attempt
to reclaim the space used by this expired data to reclaim the space used by this expired data unless the space is
immediately. Therefore, the table file is not shortened, and any at the end of the table and an exclusive lock can be obtained easily
unused space in the file is not returned to the operating on the table. Unused space at the start or middle of the file does
system. This variant of <command>VACUUM</command> can be run not result in the file being shortened and space returned to the
concurrently with normal database operations. operating system. This variant of <command>VACUUM</command> can be
run concurrently with normal database operations.
</para> </para>
<para> <para>