On Tue, Jun 16, 2009 at 7:39 PM, Aaron Turner<synfina...@gmail.com> wrote: > On Tue, Jun 16, 2009 at 2:37 PM, Alvaro > Herrera<alvhe...@commandprompt.com> wrote: >> Aaron Turner escribió: >>> I'm trying to figure out how to optimize this query (yes, I ran >>> vacuum/analyze): >>> >>> musecurity=# explain DELETE FROM muapp.pcap_store WHERE pcap_storeid >>> NOT IN (SELECT pcap_storeid FROM muapp.pcap_store_log); >> >> What PG version is this? > > Doh, just realized I didn't reply back to list. It's version 8.3.3. > > Also, pcap_storeid is unique in pcap_store_log
Speaking as one who has dealt with this frustration more than once, you can typically get better performance with something like: DELETE FROM muapp.pcap_store AS x FROM muapp.pcap_store a LEFT JOIN muapp.pcap_store_log b ON a.pcap_store_id = b.pcap_storeid WHERE x.pcap_storeid = a.pcap_storeid AND b.pcap_storeid IS NULL This is emphatically lame, but there you have it. It's first of all lame that we can't do a better job optimizing NOT-IN, at least when the expression within the subselect is known to be not-null, and it's secondly lame that the syntax of DELETE doesn't permit a LEFT JOIN without a self-JOIN. </rant> ...Robert -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
