| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <decibel(at)decibel(dot)org> |
| Cc: | Neil Conway <neilc(at)samurai(dot)com>, "A(dot) Steinmetz" <ast(at)domdv(dot)de>, pgsql-bugs <pgsql-bugs(at)postgresql(dot)org> |
| Subject: | Re: BUG #1334: PREPARE creates bad execution plan (40x |
| Date: | 2004-12-01 03:53:23 |
| Message-ID: | 893.1101873203@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
"Jim C. Nasby" <decibel(at)decibel(dot)org> writes:
> FWIW this is a hard problem; Oracle is the only database I know of
> that's tackled it.
It seems fair to point out that this is the tradeoff you must buy into
when using PREPARE. You can have a query plan that is tailored to the
specific parameter value you supply, or you can have a generic query
plan. The tailored plan will cost you planning time; the generic plan
will save you planning time; but there's no free lunch. If your table
statistics are such that you really need different plans for different
parameter values, then you shouldn't be using PREPARE. I do not think
this is a database bug --- it looks more like DBA misuse of the
available tools.
regards, tom lane
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