Re: IN vs EXISTS

Tom,

I'm using 8.3.1. I did run EXPLAIN but have never familiarized myself
with how to read/use it beside simple comparing cost estimation and
whether there is any seq scan that can benefit from creating index.

Thanks for replying

On Jun 7, 11:19 am, t(dot)(dot)(dot)(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane) wrote:
> askel <dummy(dot)(dot)(dot)(at)mail(dot)ru> writes:
> > Performance is at least few times better when EXISTS is used.
>
> It really shouldn't be. PG knows more possible plans for IN than
> EXISTS, so IN should pretty much always be equal or better ... unless
> the planner is making the wrong choice. I speculate that you have
> out-of-date statistics or some such. Have you compared EXPLAIN ANALYZE
> output for the two cases? Which PG version are we talking about?
>
> regards, tom lane
>
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