RE: [HACKERS] RE: [GENERAL] Long update query ? (also Re: [GENERAL] CNF vs. DNF)

Taral <taral@mail.utexas.edu>

From: "Taral" <taral@mail.utexas.edu>
To: "Bruce Momjian" <maillist@candle.pha.pa.us>
Cc: <jwieck@debis.com>, <hackers@postgreSQL.org>
Date: 1998-10-04T02:26:20Z
Lists: pgsql-hackers, pgsql-general
> 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