Re: Query Time

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.