improper estimates even with high statistic values
От | Robert Treat |
---|---|
Тема | improper estimates even with high statistic values |
Дата | |
Msg-id | 1137535112.27838.837.camel@camel обсуждение исходный текст |
Ответы |
Re: improper estimates even with high statistic values
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Список | pgsql-bugs |
After some extensive discussion on irc, berkus, myself and a few others think we have uncovered a possible bug, or at the least some odd behavior in > 8.1.1. It centers around my recent post to performance http://archives.postgresql.org/pgsql-performance/2006-01/msg00248.php and how I could not seem to get some of the estimates to become reasonable even after bumping up my stats target to 400 which caused every row to be analyzed. If you look at the left join and hash join estimates of the third query you'll note they seem to always get estimated to 1 for no reason that we could come up with. Someone else on irc seemed to have a similar problem to this, so we are wondering if there is some problem here. So the question really is if someone can deduce the behavior from looking at what was provided in the email? If not and you have questions let me know, otherwise I can send a chopped up test database which can reproduce the query issues off list should someone want to walk through the pg code to investigate. TIA Robert Treat -- Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL
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