From: Tom Lane <tgl@sss.pgh.pa.us>
To: weiping <laserlist@pgsqldb.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: weird query plan
Date: Wed, 06 Jun 2007 10:40:41 -0400
Message-ID: <20759.1181140841@sss.pgh.pa.us> (raw)
In-Reply-To: <46662DE7.4030602@pgsqldb.com>
References: <46662DE7.4030602@pgsqldb.com>
weiping <laserlist@pgsqldb.com> writes:
> -> Index Scan using urlusermaps_userid on wd_urlusermaps a
> (cost=0.00..6750.55 rows=1094 width=96) (actual time=0.544..5.616
> rows=41 loops=1)
> Index Cond: (userid = 219177)
> Filter: ("share" = 1)
> the userid=219177 got 2000+ record and around 40 shared=1, why above 2 query
> shows so much difference?
Probably because the rowcount estimate is so far off (1094 vs 41).
Possibly boosting the statistics target would help.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, laserlist@pgsqldb.com
Subject: Re: weird query plan
In-Reply-To: <20759.1181140841@sss.pgh.pa.us>
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