Re: Query Time

vacuum verbose;

should tell you something.

On Wed, 13 Aug 2003, Lufkin, Brad wrote:

> Is there some objective way to confirm this? (Sorry for what may seem like
> obvious questions, but I'm a newbie with psql--less than one week!)
>
> -----Original Message-----
> From: scott.marlowe [mailto:scott(dot)marlowe(at)ihs(dot)com]
> Sent: Wednesday, August 13, 2003 5:03 PM
> To: Lufkin, Brad
> Cc: 'psql'
> Subject: Re: [JDBC] Query Time
>
>
> I'd aree with Tom here that it sounds like there's lots of dead tuples in
> that table.
>
> On Wed, 13 Aug 2003, Lufkin, Brad wrote:
>
> > 30 million rows....
> >
> > -----Original Message-----
> > From: scott.marlowe [mailto:scott(dot)marlowe(at)ihs(dot)com]
> > Sent: Wednesday, August 13, 2003 4:39 PM
> > To: Lufkin, Brad
> > Cc: 'psql'
> > Subject: Re: [JDBC] Query Time
> >
> >
> > How many rows in that table? 90 seconds is a long time for a select to
> > take, period, with or without a limit.
> >
> > On Wed, 13 Aug 2003, Lufkin, Brad wrote:
> >
> > > Thanks for the info. Still, I'm surprised that a limited query would
> take
> > 90
> > > seconds.
> > >
> > > -----Original Message-----
> > > From: scott.marlowe [mailto:scott(dot)marlowe(at)ihs(dot)com]
> > > Sent: Wednesday, August 13, 2003 4:20 PM
> > > To: Lufkin, Brad
> > > Cc: 'psql'
> > > Subject: Re: [JDBC] Query Time
> > >
> > >
> > > On Wed, 13 Aug 2003, Lufkin, Brad wrote:
> > >
> > > > I'm running the following query:
> > > >
> > > > SELECT * FROM someTable LIMIT 20
> > > >
> > > > I turned on explain analyze (tip #8!) and was told that the query plan
> > was
> > > > sequential (no surprise there) with an estimated cost of between 0.00
> > and
> > > > 1.07. Surprisingly, the actual time was around 90000 msec (or
> > > one-and-a-half
> > > > minutes). What's going on?
> > >
> > > costs are estimated as a percentage of a cost of a single page access in
>
> > > sequential mode. I.e. a single sequential page access is assumed to
> cost
> > > 1.0, and everything is relative to that. The cost numbers do NOT
> > > translate directly into any time unit.
> > >
> > >
> >
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 9: the planner will ignore your desire to choose an index scan if your
> > joining column's datatypes do not match
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 8: explain analyze is your friend
> >
>