Re: Cost estimates consistently too high - does it matter?

Well, I usually am under a misapprehension! Thanks for the explanation about LIMIT too.

In that case then, I shall stop worrying and learn to love the planner.

M

> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: 08 August 2003 16:15
> To: Matt Clark
> Cc: pgsql-admin(at)postgresql(dot)org
> Subject: Re: [ADMIN] Cost estimates consistently too high - does it
> matter?
>
>
> "Matt Clark" <matt(at)ymogen(dot)net> writes:
> > I've noticed that the cost estimates for a lot of my queries are
> > consistently far to high.
>
> You seem to be under a misapprehension. The cost estimates are not
> in units of milliseconds, they are on an arbitrary scale with 1.0
> defined as one disk fetch.
>
> LIMIT throws another monkey wrench into the mix: the estimates for the
> plan nodes underneath the limit are done as if the plan were to be
> executed to completion, which of course it won't be.
>
> regards, tom lane
>
>