On Wed, 2007-10-17 at 20:37 +0100, Richard Huxton wrote:
> Ow Mun Heng wrote:
> > Query2 is way faster mainly because the plan does not choose a seq scan
> > on a table w/ >20million rows.
> > The only difference between Query 1 and query 2 is that the
> > audio_key_dtime is chosen from a table rather than provided on the
> > query.
> >
> > I'm not sure why this is the case and why it chooses such plans.
> > (should I be posting to pg-performance?)
>
> Your query plans don't seem to match your queries. That makes it
> difficult to provide meaningful advice.
>
>
Well, then that makes both you and me(both) stumped. because the 2
queries are exactly the same except for the data part.
Index Cond: ((audit_key_dtime >= $0) AND (audit_key_dtime < $1))
Index Cond: ((audit_key_dtime >= '2007-08-08 18:00:00'::timestamp without time zone)
AND (audit_key_dtime < '2007-08-08 18:01:00'::timestamp without time zone))
This is _the_ only difference between the 2 queries where on one, the
dates are provided, and the other is selected from a table.
I have no idea why the plans are so different between the two.
---------------------------(end of broadcast)---------------------------
TIP 3: Have you checked our extensive FAQ?
http://www.postgresql.org/docs/faq
