| From: | "Scott Marlowe" <smarlowe(at)qwest(dot)net> |
|---|---|
| To: | "Greg Stark" <gsstark(at)mit(dot)edu> |
| Cc: | "Jack Kerkhof" <jack(dot)kerkhof(at)guest-tek(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Why does a simple query not use an obvious index? |
| Date: | 2004-08-29 21:44:15 |
| Message-ID: | 1093815855.5493.33.camel@localhost.localdomain |
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| Thread: | |
| Lists: | pgsql-performance |
On Sun, 2004-08-29 at 15:38, Scott Marlowe wrote:
> On Sun, 2004-08-29 at 15:12, Greg Stark wrote:
> > "Scott Marlowe" <smarlowe(at)qwest(dot)net> writes:
> >
> > > Also, count(*) is likely to always generate a seq scan due to the way
> > > aggregates are implemented currently in pgsql. you might want to try:
> >
> > Huh? I'm curious to know what you're talking about here.
>
> This has been discussed ad infinitum on the lists in the past. And
> explained by better minds than mine, but I'll give it a go.
>
> PostgreSQL has a "generic" aggregate method. Imagine instead doing a
> select count(id1+id2-id3) from table where ...
that should be avg(id1+id2-id3)... doh
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