Oliver Seidel <postgresql@xxxxxxxxxxx> writes: > I have > create table x ( att bigint, val bigint, hash varchar(30) > ); > with 693million rows. The query > create table y as select att, val, count(*) as cnt from x > group by att, val; > ran for more than 2000 minutes and used 14g memory on an 8g physical > RAM machine What was the plan for that query? What did you have work_mem set to? I can believe such a thing overrunning memory if the planner chose to use a hash-aggregation plan instead of sort-and-unique, but it would only do that if it had made a drastic underestimate of the number of groups implied by the GROUP BY clause. Do you have up-to-date statistics for the source table? regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
