| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Leif B(dot) Kristensen" <leif(at)solumslekt(dot)org> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Sequential scan from simple query |
| Date: | 2007-05-23 14:44:25 |
| Message-ID: | 20578.1179931465@sss.pgh.pa.us |
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| Lists: | pgsql-general |
"Leif B. Kristensen" <leif(at)solumslekt(dot)org> writes:
> Can anybody tell me why the following query requires a full table scan?
> pgslekt=> explain select person_id, last_edit from persons
> order by last_edit desc, person_id desc limit 50;
> 'persons' is a regular table where person_id is the primary
> key. 'last_edit' is a regular date field. I've also tried:
> pgslekt=> create index last_edit_key on persons(last_edit);
> But that doesn't make any difference.
Neither of those indexes can provide the requested two-column ordering.
regards, tom lane
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