[postgis-users] Postgres Tuning - Actual Results

[Stephen Frost]

Brian,

* Brian Hamlin (maplabs at light42.com) wrote:
> I am guessing that work_mem is the wildcard that is causing the
> large allocations..
> Comments / Suggestions on this ?

Yes, work_mem is used to determine, for each sort/hash/etc, if it
should be done in-memory or done on disk.  If you have a huge query,
with many sorts/hashes/etc, a single query could use much more than the
value of work_mem.

If you reduce work_mem, PG will try to find another plan where each
sort/hash/etc fits within that constraint, which may mean some spilling
to disk and/or overall change in the plan.

	Thanks,

		Stephen
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