| From: | "Jim C(dot) Nasby" <decibel(at)decibel(dot)org> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: How are foreign key constraints built? |
| Date: | 2005-01-25 02:30:58 |
| Message-ID: | 20050125023058.GS67721@decibel.org |
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| Thread: | |
| Lists: | pgsql-general |
On Mon, Jan 24, 2005 at 09:24:49AM -0500, Greg Stark wrote:
> "Jim C. Nasby" <decibel(at)decibel(dot)org> writes:
>
> > Well, every other database I've used can do index covering, which means
> > index scans *are* faster.
>
> Still not necessarily true. In a case like this it would still be random
> access which would be slower than sequential access.
Actually, even with random access, a covering index can still be faster.
Imagine a single-field index on a table with 40 fields.
--
Jim C. Nasby, Database Consultant decibel(at)decibel(dot)org
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