Re: Query Time

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