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Re: Relations summary at end of vacuum

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Doug Y <dylists(at)ptd(dot)net>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: Relations summary at end of vacuum
Date: 2004-10-18 18:06:52
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Lists: pgsql-admin
Doug Y <dylists(at)ptd(dot)net> writes:
>   What exactly are the "Relations"  that are referred to in the summary 
> at the end of a vacuum?

Tables and indexes.

> I have two DBs that are supposed to be mirrored copies of each other,
> but my relation & page counts are different for each after a vacuum:

IIRC, a relation won't get entered into the free space map at all if
no useful free space is found by VACUUM.  So if the only thing that ever
happens on the mirror is insertion of new rows, I could believe that
there would be many fewer active FSM entries than for the master.

However the fact that the database with fewer FSM relations knows about
more free pages within those tables seems a bit at variance with that
idea.  Maybe your mirror is insert-only for some tables and not others,
and you've been lax about vacuuming the mirror?

			regards, tom lane

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