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Re: Why this Query Plan is different

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 (view raw or flat)
Thread:
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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