Re: Table using more disk space than expected

From: Francisco Olarte <folarte(at)peoplecall(dot)com>
To: Steve Pritchard <steve(dot)pritchard(at)bto(dot)org>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: Table using more disk space than expected
Date: 2015-09-23 17:46:32
Message-ID: CA+bJJbxKuKBu+sBbWH_xBD18PVqtxv9V1i_5Vgmxw+bpOC=y6A@mail.gmail.com
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Hi Steve:

On Wed, Sep 23, 2015 at 7:25 PM, Steve Pritchard
<steve(dot)pritchard(at)bto(dot)org> wrote:
> I thought that autovacuum should recover the free space, however I see now
> from the documentation that it doesn't (and that this is deliberate):
....
> I'll do a VACUUM FULL, which I expect to reduce table_len.

Full is for when you've done a drastic reduction on a table. Some
tables oscillate in size, grow and shrink and regrow.., those do not
benefit of vacuum full on the long run, because if you have a table
which oscilates between , let's say, 10G and 20G you need 20G of disk
space, if you shrink and fill the rest with other uses server will
crash on next growth ( some very special cases may be different, but
in general if you have free space is because you create/delete, be it
directly or via MVCC updates, so having it there for next usage is not
so bad ).

Francisco Olarte.

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