| From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | daveh(at)insightdist(dot)com (David Hartwig) |
| Cc: | taral(at)mail(dot)utexas(dot)edu, jwieck(at)debis(dot)com, hackers(at)postgreSQL(dot)org |
| Subject: | Re: [HACKERS] RE: [GENERAL] Long update query ? (also Re: [GENERAL] CNF vs. DNF) |
| Date: | 1998-10-07 17:56:18 |
| Message-ID: | 199810071756.NAA02839@candle.pha.pa.us |
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| Thread: | |
| Lists: | pgsql-general pgsql-hackers |
> The problem is that you cannot depend upon factoring to reduce these complex
> statements. We need to retain a place holder (pointer) for each passed
> parameter. Otherwise we need to re-(parse and plan) the statement before each
> execution; thus, loosing one of the major benefits of PREPARE.
I think we already have such a problem. When using optimization
statistics, the optimizer checks the value of the constant to determine
how many rows will be returned by a "x > 10" by looking at the min/max
values for the column. Prepared queries where this value will change
would make that a problem.
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
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