Tom Lane wrote:
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
Hi Tom,
Actually this is
show server_version;
server_version
----------------
8.2.5
On FreeBSD 6.2
And Daniel gave me a query that does the job in just a few seconds.
Thanks,
Steve
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