Re: eliminating records not in (select id ... so SLOW?

On Fri, 01 Aug 2008 10:33:59 -0400
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Ivan Sergio Borgonovo <mail(at)webthatworks(dot)it> writes:
> > Well I reached 3Gb of work_mem and still I got:
>
> > "Seq Scan on catalog_categoryitem (cost=31747.84..4019284477.13
> > rows=475532 width=6)"
> > " Filter: (NOT (subplan))"
> > " SubPlan"
> > " -> Materialize (cost=31747.84..38509.51 rows=676167
> > width=8)" " -> Seq Scan on catalog_items
> > (cost=0.00..31071.67 rows=676167 width=8)"
>
> Huh. The only way I can see for that to happen is if the datatypes
> involved aren't hashable. What's the datatypes of the two columns
> being compared, anyway?

I changed both columns to bigint.
I added 2 indexes on the ItemID column of both tables and increased
work_mem to 3Gb [sic].
The query got executed in ~1300ms... but explain gave the same
output as the one above.

The problem is solved... but curious mind want to know.

--
Ivan Sergio Borgonovo
http://www.webthatworks.it