Re: Unexpected sequence scan

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От
Kevin Grittner
Тема
Re: Unexpected sequence scan
Дата
в 11:40:58
Msg-id
4FA3A410020000250004787C@gw.wicourts.gov
Ответ на
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Unexpected sequence scan Dan Fairs <dan.fairs@gmail.com>
Re: Unexpected sequence scan "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
Re: Unexpected sequence scan Tom Lane <tgl@sss.pgh.pa.us>
Re: Unexpected sequence scan Dan Fairs <dan.fairs@gmail.com>
Dan Fairs  wrote:
 
> I have a query which is running slowly, and the query plan shows
> an unexpected sequence scan where I'd have expected the planner to
> use an index. 
 
Looking at the actual row counts compared to run time, it appears
that the active portion of your data set is heavily cached.  In such
an environment, I would add these lines to postgresql.conf, to
better model costs:
 
seq_page_cost = 0.1
random_page_cost = 0.1  # or maybe slightly higher
cpu_tuple_cost = 0.03
 
-Kevin
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