From: | Gregory Stark <stark(at)enterprisedb(dot)com> |
---|---|
To: | "Robert Haas" <robertmhaas(at)gmail(dot)com> |
Cc: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Josh Berkus" <josh(at)agliodbs(dot)com>, "Greg Smith" <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Simple postgresql.conf wizard |
Date: | 2008-11-27 23:46:35 |
Message-ID: | 87ej0wn350.fsf@oxford.xeocode.com |
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Lists: | pgsql-hackers |
"Robert Haas" <robertmhaas(at)gmail(dot)com> writes:
> ANALYZE with default_statistics_target set to 10 takes 13 s. With
> 100, 92 s. With 1000, 289 s.
That is interesting. It would also be interesting to total up the time it
takes to run EXPLAIN (without ANALYZE) for a large number of queries.
I did start looking at running the experiment Tom was asking for with DBT3
data sets but, uh, the most recent dbt-3 data generation source I could find
was four years old. Is there an active source repository for this stuff?
> Given the amount of clamor for a higher value for
> default_statistics_target, I'm a little surprised by these results.
> It may be that the queries I'm running are not ones for which more
> statistics generate better plans, but I think they really are
> representative of what we run. Maybe someone could suggest some types
> of query that would be likely to helped by better statistics?
I think there are a lot of variables here. One is the distribution of the
data. Your data sounds like it's reasonably evenly distributed.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's 24x7 Postgres support!
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