Re: cluster test

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Joachim Wieland <joe(at)mcknight(dot)de>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: cluster test
Date: 2007-05-25 21:58:58
Message-ID: 23613.1180130338@sss.pgh.pa.us
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Joachim Wieland <joe(at)mcknight(dot)de> writes:
> SET enable_bitmapscan = 0;
> EXPLAIN SELECT conname FROM pg_constraint WHERE conrelid = 'clstr_tst'::regclass;
> QUERY PLAN
> ---------------------------------------------------------------
> Seq Scan on pg_constraint (cost=0.00..27.15 rows=1 width=64)
> Filter: (conrelid = 54538::oid)
> (2 rows)

Hm, well, that's why it doesn't want to use a seqscan, but why is the
estimate so high? I get 7.35 on my boxes, vs 8.27 (which does agree
with yours) for the indexscans. Stranger and stranger.

Would you try inserting a "vacuum verbose pg_constraint" into the test
as well? Maybe that will tell something relevant.

regards, tom lane

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