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Re: [GENERAL] Long update query ?

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: taral(at)mail(dot)utexas(dot)edu (Taral)
Cc: daveh(at)insightdist(dot)com, ser(at)nsu(dot)ru, pgsql-general(at)postgreSQL(dot)org
Subject: Re: [GENERAL] Long update query ?
Date: 1998-10-01 22:54:19
Message-ID: 199810012254.SAA18974@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
[Charset iso-8859-1 unsupported, filtering to ASCII...]
> > This is caused by a semi-well known weakness in the optimizer.
> > The optimizer
> > rewrites the WHERE clause in conjunctive normal form (CNF):
> >
> >    (A and B) or (C and D) ==>  (A or C) and (A or D) and (B or C)
> > and (B or D)
> >
> 
> Wouldn't disjunctive normal form be better, since it can be implemented as
> the simple union of a set of small queries?

Please tell us more.

-- 
  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
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026


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