On Tue, Oct 16, 2012 at 08:19:43PM -0400, Chris Ruprecht wrote:
>
> On Oct 16, 2012, at 20:01 , Evgeny Shishkin <[email protected]> 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 <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
--
Sent via pgsql-performance mailing list ([email protected])
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
