Re: 8.4/9.0 simple query performance regression - Mailing list pgsql-performance

07.06.11 00:45, Josh Berkus написав(ла):
> All,
>
> Just got this simple case off IRC today:
>
> 8.4.4
> This plan completes in 100ms:
>     Filter: (NOT (hashed SubPlan 1))

> 9.0.2
> This plan does not complete in 15 minutes or more:
>     Filter: (NOT (SubPlan 1))
"Hashed" is the key. Hashed subplans usually has much better performance.
You need to increase work_mem. I suppose it is in default state as you
need not too much memory for hash of 70K integer values.
BTW: Why do it want to materialize a result of seq scan without filter.
I can see no benefits (or is it more narrow rows?)

Best regards, Vitalii Tymchyshyn