| From: | "Taral" <taral(at)mail(dot)utexas(dot)edu> |
|---|---|
| To: | "Bruce Momjian" <maillist(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | <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: | 1998-10-04 02:26:20 |
| Message-ID: | 000501bdef3e$5f5293a0$3b291f0a@taral |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general pgsql-hackers |
> however if A and C are identical, this could become:
>
> (A OR A) AND (A OR D) AND (B OR A) AND (B OR D)
>
> and A OR A is A:
>
> A AND (A OR D) AND (B OR A) AND (B OR D)
>
> and since we are now saying A has to be true, we can remove OR's with A:
>
> A AND (B OR D)
Very nice... and you could do that after each iteration of the rewrite,
preventing the size from getting too big. :)
I have a symbolic expression tree evaluator that would be perfect for
this... I'll see if I can't adapt it.
Can someone mail me the structures for expression trees? I don't want to
have to excise them from the source. Please?
Taral
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