From: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> |
---|---|
To: | Q(at)ping(dot)be |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: vacuum does not reclaim rows |
Date: | 2003-07-05 23:38:18 |
Message-ID: | 20030706.083818.112625481.t-ishii@sra.co.jp |
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Thread: | |
Lists: | pgsql-hackers |
> > Does anybody know why vacuum full does not relcaim deleted rows if a
> > open transaction which started before the deletion happens is running
> > even on a different database?
>
> On what do you base that it doesn't reclaim those rows?
test=# vacuum full verbose t1;
INFO: --Relation public.t1--
INFO: Pages 1: Changed 1, reaped 0, Empty 0, New 0; Tup 1: Vac 0, Keep/VTL 1/0, UnUsed 0, MinLen 32, MaxLen 32; Re-using: Free/Avail. Space 8136/8136; EndEmpty/Avail. Pages 0/1.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO: Rel t1: Pages: 1 --> 1; Tuple(s) moved: 0.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
VACUUM
Here you can see "Pages: 1 --> 1; Tuple(s) moved: 0", it indicates
vacuum actually skips the table and does not reclaim those rows.
Here is a case when vacuum does reclaim.
test=# vacuum full verbose t1;
INFO: --Relation public.t1--
INFO: Pages 1: Changed 0, reaped 1, Empty 0, New 0; Tup 0: Vac 1, Keep/VTL 0/0, UnUsed 0, MinLen 0, MaxLen 0; Re-using: Free/Avail. Space 8168/0; EndEmpty/Avail. Pages 1/0.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO: Rel t1: Pages: 1 --> 0.
VACUUM
--
Tatsuo Ishii
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