Steve Clark <sclark@xxxxxxxxxxxxx> writes: > Tom Lane wrote: >> Also, whatever is the ORDER BY for? > without the order by it wants to do a seq scan of t_unit_event_log. > see below: > explain select count(*) from t_event_ack_log where event_log_no not > in (select event_log_no from t_unit_event_log); > QUERY PLAN > ---------------------------------------------------------------------------------------- > Aggregate (cost=12144872193.82..12144872193.82 rows=1 width=0) > -> Seq Scan on t_event_ack_log (cost=0.00..12144871485.07 > rows=283497 width=0) > Filter: (NOT (subplan)) > SubPlan > -> Seq Scan on t_unit_event_log (cost=0.00..40286.56 > rows=1021156 width=4) > (5 rows) Hmm, the big problem with that isn't the seqscan but the lack of a Materialize step to buffer it; which says to me that you're running a pretty old Postgres version (8.0 or older). You should think about an update if you're running into performance issues. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
