Re: Lazy vacuum space reclaiming
От | Bruce Momjian |
---|---|
Тема | Re: Lazy vacuum space reclaiming |
Дата | |
Msg-id | 200512070536.jB75aCm14675@candle.pha.pa.us обсуждение исходный текст |
Ответ на | Lazy vacuum space reclaiming ("Jim C. Nasby" <jnasby@pervasive.com>) |
Список | pgsql-docs |
Adjustment patch applied. Thanks. --------------------------------------------------------------------------- Jim C. Nasby wrote: > >From http://www.postgresql.org/docs/8.0/interactive/maintenance.html: > > "The first form, known as "lazy vacuum" or just VACUUM, marks expired > data in tables and indexes for future reuse; it does not 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 isn't completely accurate, though I'm not sure what a good wording > would be. Maybe: > > "The first form, known as "lazy vacuum" or just VACUUM, marks expired > data in tables and indexes for future reuse. It only reclaims expired > space from tables if it is at the end of the table, and no empty space > is reclaimed from indexes." > -- > Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com > Pervasive Software http://pervasive.com work: 512-231-6117 > vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 > > ---------------------------(end of broadcast)--------------------------- > TIP 3: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq > -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 Index: doc/src/sgml/maintenance.sgml =================================================================== RCS file: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v retrieving revision 1.51 diff -c -c -r1.51 maintenance.sgml *** doc/src/sgml/maintenance.sgml 4 Nov 2005 23:14:00 -0000 1.51 --- doc/src/sgml/maintenance.sgml 7 Dec 2005 05:35:08 -0000 *************** *** 141,151 **** 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. </para> <para> --- 141,152 ---- 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 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>
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