Re: Index optimization ?
От | Ragnar Hafstað |
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Тема | Re: Index optimization ? |
Дата | |
Msg-id | 1105894541.32063.22.camel@localhost.localdomain обсуждение исходный текст |
Ответ на | Re: Index optimization ? (Bo Lorentsen <bl@netgroup.dk>) |
Ответы |
Re: Index optimization ?
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Список | pgsql-general |
On Sun, 2005-01-16 at 17:45 +0100, Bo Lorentsen wrote: > Ragnar Hafstað wrote: > >when a volatile function is used thus: > > SELECT * FROM mytable WHERE col=myvolatilefunc(); > >the planner must call the function once per table row, and assume > >possibly different return values each time, so an indexscan will > >not improve timings. > > > > > Why not use the index scan for every row, is this a "limit" in the > planner ? I think there is something in the planner I don't understand :-) the planner will just use the plan it estimates will be fastest. because of how indexscans work in postgresql, in this case it would be slower than a tablescan (assuming the function really is volatile) gnari
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