Re: The planner chooses seqscan+sort when there is an
От | Csaba Nagy |
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Тема | Re: The planner chooses seqscan+sort when there is an |
Дата | |
Msg-id | 1146674520.14093.185.camel@coppola.muc.ecircle.de обсуждение исходный текст |
Ответ на | Re: The planner chooses seqscan+sort when there is an ("John D. Burger" <john@mitre.org>) |
Ответы |
Re: The planner chooses seqscan+sort when there is an
Re: The planner chooses seqscan+sort when there is an Re: The planner chooses seqscan+sort when there is an |
Список | pgsql-general |
> Docs say: > > > Enables or disables the query planner's use of sequential scan plan > > types. It's not possible to suppress sequential scans entirely, but > > turning this variable off discourages the planner from using one if > > there are other methods available. > > Note the second sentence. Again, I think it will have to scan the > whole table anyway, because that's what you've asked for, and given > that, enable_seqscan=off doesn't apply. OK, maybe that's the point... the "cost bust" given to the sequential scan by enable_seqscan=off is not enough in this case to exceed the cost of the index scan ? The table is quite big, might be possible. I still wonder why would be seqscan+sort faster than index scan... the sort will for sure have to write to disk too given the size of the table... Cheers, Csaba.
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