| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
| Cc: | Tambet Matiisen <t(dot)matiisen(at)aprote(dot)ee>, josh(at)agliodbs(dot)com, Bill Chandler <billybobc1210(at)yahoo(dot)com>, pgsql-perform <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Question on REINDEX |
| Date: | 2005-04-19 18:34:35 |
| Message-ID: | 23413.1113935675@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> writes:
> Am I right in thinking that vacuum does at least two passes: one
> front-to-back to find removable tuples, and other back-to-front for
> movement?
VACUUM FULL, yes. VACUUM only does the first one.
> I know maintenance_work_mem is used for storing TIDs of to-be-moved
> tuples for index cleanup ... how does it relate to the above?
TIDs of to-be-deleted tuples, actually. Movable tuples aren't stored,
they're just found on-the-fly during the back-to-front pass.
regards, tom lane
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