Re: bad estimates
От | Sean Chittenden |
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Тема | Re: bad estimates |
Дата | |
Msg-id | 20030829163613.GA51475@perrin.nxad.com обсуждение исходный текст |
Ответ на | Re: bad estimates (Ken Geis <kgeis@speakeasy.org>) |
Ответы |
Re: bad estimates
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Список | pgsql-performance |
> >If you want both the max and the min, then things are going to be a > >bit more work. You are either going to want to do two separate > >selects or join two selects or use subselects. If there aren't > >enough prices per stock, the sequential scan might be fastest since > >you only need to go through the table once and don't have to hit > >the index blocks. > > > >It is still odd that you didn't get a big speed up for just the min though. > > I found I'm suffering from an effect detailed in a previous thread titled > > Does "correlation" mislead the optimizer on large tables? I don't know about large tables, but this is a big problem and something I'm going to spend some time validating later today. I think Manfred's patch is pretty good and certainly better than where we are but I haven't used it yet to see if it's the magic ticket for many of these index problems. -sc -- Sean Chittenden
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