From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | tgunasekara(at)openworld(dot)org |
Cc: | "PGSQL Admin" <pgsql-admin(at)postgresql(dot)org> |
Subject: | Re: Why this Query Plan is different |
Date: | 2005-03-24 05:59:29 |
Message-ID: | 23424.1111643969@sss.pgh.pa.us |
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Lists: | pgsql-admin |
"Thilina Gunasekara" <tgunasekara(at)openworld(dot)org> writes:
> I have two PostgreSQL Database Servers running on Gentoo which versions are
> PostgreSQL 7.4.5 (Box A) and PostgreSQL 7.3.9 (Box B)
> Due to a recent query posted by a developer I was interested to know which
> factors are affecting these two servers to behave in a different manner to
> the same query. Please shed light on this.
7.4 knows a great deal more about optimizing IN queries than 7.3 does.
I think you have misidentified the two query plans, because "Hash IN
Join" is not a plan type that 7.3 has at all. What is not clear to me
is which version is really slower. Could we see EXPLAIN ANALYZE output
(correctly labeled ;-)) not just EXPLAIN?
regards, tom lane
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