Re: Subquery WHERE IN or WHERE EXISTS faster?

On Sat, Jun 28, 2008 at 10:53 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Ulrich <ulrich(dot)mierendorff(at)gmx(dot)net> writes:
>> People say that [EXISTS is faster]
>
> People who say that are not reliable authorities, at least as far as
> Postgres is concerned. But it is always a bad idea to extrapolate
> results on toy tables to large tables --- quite aside from measurement
> noise and caching issues, the planner might pick a different plan when
> faced with large tables. Load up a realistic amount of data and then
> see what you get.
>

i've made some queries run faster using EXISTS instead of large IN
clauses... actually, it was NOT EXISTS replacing a NOT IN

while i'm not telling EXISTS is better i actually know in some cases is better

--
Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Guayaquil - Ecuador
Cel. (593) 87171157