Re: Compression and on-disk sorting

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Martijn van Oosterhout <kleptog(at)svana(dot)org>
Cc: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, Zeugswetter Andreas DCP SD <ZeugswetterA(at)spardat(dot)at>, Greg Stark <gsstark(at)mit(dot)edu>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Rod Taylor <pg(at)rbt(dot)ca>, "Bort, Paul" <pbort(at)tmwsystems(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Compression and on-disk sorting
Date: 2006-05-19 13:42:59
Message-ID: 28599.1148046179@sss.pgh.pa.us
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Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> However, postgres tables are very highly compressable, 10-to-1 is not
> that uncommon. pg_proc and pg_index compress by that for example.
> Indexes compress even more (a few on my system compress 25-to-1 but
> that could just be slack space, the record being 37-to-1
> (pg_constraint_conname_nsp_index)).

Anything containing a column of type "name" will compress amazingly well
because of all the padding spaces. I don't think that's representative
of user data though ... except maybe for the occasional novice using
"char(255)" ...

regards, tom lane

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