Re: Random plan selection in DBT-3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Random plan selection in DBT-3
Date: 2008-01-07 02:54:49
Message-ID: 2069.1199674489@sss.pgh.pa.us
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ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> I tested 8.3beta4 with DBT-3 (TPC-H) and found unstable selection of plans.
> Planner randomly selected two types of plans (A, B) when I repeated EXPLAIN.

Are you sure the statistics weren't changing underneath you (due to
auto-vacuum or auto-analyze)?

regards, tom lane

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