>Have you run ANALYZE recently? You might be running into the well-known
>problem that hashed aggregation can consume an arbitrary amount of
>memory -- posting the EXPLAIN for the query would confirm that.
>
>-Neil
>
>
>
yes, I run VACUUM ANALYZE VERBOSE then run the query,
and finally got the out of memory error.
After that, we dig in the archive and find a solution:
issue a 'set enable_hashagg=off' and re-run the query,
and now the query give me the result.
regards laser