stiening@comcast.net writes:
> The query:
> SELECT pts_key,count(*)
> FROM tm_tm_pairs GROUP BY pts_key HAVING count(*) !=1 ORDER BY
> pts_key
> Which is executed as:
> GroupAggregate (cost=108680937.80..119278286.60 rows=470993280 width=4)
> Filter: (count(*) <> 1)
> -> Sort (cost=108680937.80..109858421.00 rows=470993280 width=4)
> Sort Key: pts_key
> -> Seq Scan on tm_tm_pairs (cost=0.00..8634876.80 rows=470993280
> width=4)
> uses all available memory (32GB). pts_key is an integer and the table
> contains about 500 million rows.
That query plan doesn't look like it should produce any undue memory
consumption on the server side. How many distinct values of pts_key are
there, and what are you using to collect the query result client-side?
psql, for instance, would try to absorb the whole query result
in-memory, so there'd be a lot of memory consumed by psql if there are
a lot of pts_key values. (You can set FETCH_COUNT to alleviate that.)
A different line of thought is that you might have set work_mem to
an unreasonably large value --- the sort step will happily try to
consume work_mem worth of memory.
regards, tom lane
