wickro <robwick...@gmail.com> writes: > Hi everyone, > > I have a largish table (> 8GB). I'm doing a very simple single group > by on. I am the only user of this database. If I set work mem to > anything under 2GB (e.g. 1900MB) the postmaster process stops at that > value while it's peforming it's group by. There is only one hash > operation so that is what I would expect. But anything larger and it > eats up all memory until it can't get anymore (around 7.5GB on a 8GB > machine). Has anyone experienced anything of this sort before.
What does EXPLAIN say for both cases? I suspect what's happening is that the planner is estimating it will need 2G to has all the values and in fact it would need >8G. So for values under 2G it uses a sort and not a hash at all, for values over 2G it's trying to use a hash and failing. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training! -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
