Re: Query too slow with "not in" condition [Resolved]

Thanks a lot.

On Sun, Nov 30, 2008 at 11:28 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "David Rowley" <dgrowley(at)gmail(dot)com> writes:
> > I assume workmem, effective_cache_size and random_page_cost are all the
> same
> > in the 2 postgresql.conf?
>
> Indeed, work_mem is probably the problem. The critical difference
> between the two plans seems to be that the first one is using a
> "hashed subplan" and the second one isn't. Assuming the same datatypes in
> both databases, the only reason not to use a hashed subplan is if the
> hashtable is estimated not to fit in work_mem.
>

I changed work_mem in test machine to be implemented in production server
later. Completely forgot that when faced with this issue. Sorry for the
trouble.

I learnt about "hashed subplan" requiring sufficient work_mem, however.

Thanks and regards,

Ma Sivakumar

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