Re: Poor performance o

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Craig A(dot) James" <cjames(at)modgraph-usa(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Poor performance o
Date: 2006-03-22 04:31:43
Message-ID: 10012.1143001903@sss.pgh.pa.us
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"Craig A. James" <cjames(at)modgraph-usa(dot)com> writes:
> Tom Lane wrote:
>> Given the sizes of the tables involved, you'd likely have to boost up
>> work_mem before the planner would consider a hash join. What nondefault
>> configuration settings do you have, anyway?

> shared_buffers = 20000
> work_mem = 32768
> effective_cache_size = 300000

So for a 6M-row table, 32M work_mem would allow ... um ... 5 bytes per
row. It's not happening :-(

Try boosting work_mem by a factor of 100 and seeing whether a hash-based
join actually wins or not. If so, we can discuss where the sane setting
really falls, if not there's no point.

regards, tom lane

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