From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Ow Mun Heng <Ow(dot)Mun(dot)Heng(at)wdc(dot)com> |
Cc: | Richard Huxton <dev(at)archonet(dot)com>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Poor Plan selected w/ not provided a date/time but selecting date/time from a table |
Date: | 2007-10-18 11:21:13 |
Message-ID: | 20071018112113.GH5737@alvh.no-ip.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
Ow Mun Heng wrote:
>
> On Wed, 2007-10-17 at 22:47 -0300, Alvaro Herrera wrote:
> > Ow Mun Heng wrote:
> >
> > > 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.
> >
> > The difference is that it has to consider the worst possibility in the
> > second case, whereas the other one knows the interval is just one minute.
>
> Actually the dates are just 1 min apart in both cases.
Of course. My point is that the planner doesn't know that in the first
case.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
From | Date | Subject | |
---|---|---|---|
Next Message | Bill Moran | 2007-10-18 12:24:49 | Re: a failover scenario |
Previous Message | Tomi N/A | 2007-10-18 10:15:44 | a failover scenario |