On Oct 12, 2007, at 4:09 PM, henk de wit wrote:
> > It looks to me like you have work_mem set optimistically large. This
> > query seems to be doing *many* large sorts and hashes:
>
> I have work_mem set to 256MB. Reading in PG documentation I now
> realize that "several sort or hash operations might be running in
> parallel". So this is most likely the problem, although I don't
> really understand why memory never seems to increase for any of the
> other queries (not executed in a transaction). Some of these are at
> least the size of the query that is giving problems.
Wow. That's inordinately high. I'd recommend dropping that to 32-43MB.
>
> Btw, is there some way to determine up front how many sort or hash
> operations will be running in parallel for a given query?
Explain is your friend in that respect.
Erik Jones
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