From: Rural Hunter <ruralhunter@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-admin@postgresql.org
Subject: Re: wrong count estimation in query plan
Date: Fri, 31 Oct 2014 21:33:08 +0800
Message-ID: <54538F94.3010507@gmail.com> (raw)
In-Reply-To: <19884.1414679157@sss.pgh.pa.us>
References: <5451E60A.60009@gmail.com>
<19884.1414679157@sss.pgh.pa.us>
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在 2014/10/30 22:25, Tom Lane 写道:
> If ANALYZE doesn't scan the entire table then it updates the rowcount
> estimate using a moving-average approach, rather than assuming that
> the blocks it did look at are necessarily completely representative.
> That causes the estimate to converge over multiple passes. Since it
> took so many cycles to get close to reality, we can conclude that the
> table is several times larger than the number of blocks ANALYZE is
> willing to sample ... which, for a table with only 1000 rows in it,
> says you've got a bad table-bloat problem. VACUUM FULL or CLUSTER
> might be indicated. regards, tom lane
Got it. A vacuum solved the problem. Thanks.
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To: pgsql-admin@postgresql.org
Cc: ruralhunter@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: wrong count estimation in query plan
In-Reply-To: <54538F94.3010507@gmail.com>
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