| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, 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: | 2006-05-26 20:21:44 |
| Message-ID: | 1148674904.2755.254.camel@localhost.localdomain |
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| Lists: | pgsql-hackers |
On Fri, 2006-05-26 at 14:47 -0500, Jim C. Nasby wrote:
> But the meat is:
> -- work_mem --
> Scale 2000 20000
> not compressed 150 805.7 797.7
> not compressed 3000 17820 17436
> compressed 150 371.4 400.1
> compressed 3000 8152 8537
> compressed, no headers 3000 7325 7876
Since Tom has committed the header-removing patch, we need to test
not compressed, no headers v compressed, no headers
There is a noticeable rise in sort time with increasing work_mem, but
that needs to be offset from the benefit that in-general comes from
using a large Heap for the sort. With the data you're using that always
looks like a loss, but that isn't true with all input data orderings.
--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com
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