Re: Poor performance o

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: "Craig A. James" <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Date: 2006-03-22T04:31:43Z
Lists: pgsql-hackers, pgsql-performance
"Craig A. James" <cjames@modgraph-usa.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