| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Jeroen T(dot) Vermeulen" <jtv(at)xs4all(dot)nl> |
| Cc: | "Gregory Stark" <stark(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Optimizing prepared statements |
| Date: | 2006-09-04 16:03:50 |
| Message-ID: | 25122.1157385830@sss.pgh.pa.us |
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"Jeroen T. Vermeulen" <jtv(at)xs4all(dot)nl> writes:
> On Sun, September 3, 2006 23:52, Tom Lane wrote:
>> What exactly do you mean by "optimize away a parameter"? The way you
>> described the mechanism, there are no parameters that are "optimized
>> away", you've merely adjusted selectivity predictions using some assumed
>> values.
> I'm using "optimized away" as shorthand for "replaced with a literal
> constant in the statement definition used to generate the plan."
Ah. I think you're confusing the spectators by using "predict" when you
should say "match". You're looking for previously generated plans that
have assumed parameter values matching the current query --- saying that
the plan "predicts" a parameter value is just a really poor choice of
wording.
regards, tom lane
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