Adam Rich <ada...@sbcglobal.net> writes: > Please reference these explain plans. This is Pg 8.4.1
> http://explain-analyze.info/query_plans/4032-query-plan-2745 > http://explain-analyze.info/query_plans/4033-query-plan-2746 > First, could somebody explain what is leading the first query to choose > a different plan that's much slower? I think it's rejecting the HashAggregate plan because, with the estimated-wider rows, the hash table is estimated to exceed work_mem. > Second, why would it choose to sort on disk for what appears to be ~32MB > of data, when my work_mem and temp_buffers are both 64 MB each? The on-disk representation is more compact for various reasons. > But it's only reporting 92kb of memory used? Why don't I see numbers > between 64 MB and 128 MB for both the on-disk and in-memory plans? You're not taking into account whether the sort is on pre-aggregation or post-aggregation data. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
