| From: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
|---|---|
| To: | Neil Conway <neilc(at)samurai(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: detecting poor query plans |
| Date: | 2003-11-26 17:38:47 |
| Message-ID: | 20031126173847.GA15041@dcc.uchile.cl |
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| Lists: | pgsql-hackers |
On Wed, Nov 26, 2003 at 11:59:33AM -0500, Neil Conway wrote:
> > In some situations that doesn't really matter, as the same plan
> > would have gotten picked anyway.
>
> The hint is NOT "the chosen plan was non-optimal"; the hint is "the
> query planner did not produce an accurate row count estimate for this
> node in the query tree."
Maybe it could only be done for SeqScan and IndexScan nodes, which are
probably the most common source of bad estimates related to poor
statistics.
--
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
"At least to kernel hackers, who really are human, despite occasional
rumors to the contrary" (LWN.net)
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