From: Tom Lane <tgl@sss.pgh.pa.us>
To: Huang, Suya <Suya.Huang@au.experian.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: same query different execution plan (hash join vs. semi-hash join)
Date: Mon, 19 May 2014 10:22:17 -0400
Message-ID: <868.1400509337@sss.pgh.pa.us> (raw)
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"Huang, Suya" <Suya.Huang@au.experian.com> writes:
> Thank you Tom. But the time spent on scanning table test1 is less than 1 second (91.738 compares to 87.869), so I guess this shouldn't be the issue?
No, the point is that the bad rowcount estimate (and, possibly, lack of
stats about join column contents) causes the planner to pick a join method
that's not ideal for this query.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, Suya.Huang@au.experian.com
Subject: Re: same query different execution plan (hash join vs. semi-hash join)
In-Reply-To: <868.1400509337@sss.pgh.pa.us>
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