On Tue, Oct 16, 2012 at 08:19:43PM -0400, Chris Ruprecht wrote: > > On Oct 16, 2012, at 20:01 , Evgeny Shishkin <itparanoia@xxxxxxxxx> wrote: > > > Selecting 5 yours of data is not selective at all, so postgres decides it is cheaper to do seqscan. > > > > Do you have an index on patient.dnsortpersonnumber? Can you post a result from > > select count(*) from patient where dnsortpersonnumber = '347450'; ? > > > > Yes, there is an index: > > "Aggregate (cost=6427.06..6427.07 rows=1 width=0)" > " -> Index Scan using patient_pracsortpatientnumber on patient (cost=0.00..6427.06 rows=1 width=0)" > " Index Cond: (dnsortpersonnumber = '347450'::text)" > > > In fact, all the other criteria is picked using an index. I fear that the >= and <= on the timestamp is causing the issue. If I do a "=" of just one of them, I get an index scan. But I need to scan the entire range. I get queries like "give me everything that was entered into the system for this patient between these two dates". A single date wouldn't work. Have you read our FAQ on this matter? http://wiki.postgresql.org/wiki/FAQ#Why_are_my_queries_slow.3F_Why_don.27t_they_use_my_indexes.3F -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
