From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | taral(at)mail(dot)utexas(dot)edu (Taral) |
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: | 1998-10-02 21:39:05 |
Message-ID: | 199810022139.RAA21082@candle.pha.pa.us |
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Lists: | pgsql-general pgsql-hackers |
[Charset iso-8859-1 unsupported, filtering to ASCII...]
> > Another idea is that we rewrite queries such as:
> >
> > SELECT *
> > FROM tab
> > WHERE (a=1 AND b=2 AND c=3) OR
> > (a=1 AND b=2 AND c=4) OR
> > (a=1 AND b=2 AND c=5) OR
> > (a=1 AND b=2 AND c=6)
> >
> > into:
> >
> > SELECT *
> > FROM tab
> > WHERE (a=1 AND b=2) AND (c=3 OR c=4 OR c=5 OR c=6)
>
> Very nice, but that's like trying to code factorization of numbers... not
> pretty, and very CPU intensive on complex queries...
Yes, but how large are the WHERE clauses going to be? Considering the
cost of cnfify() and UNION, it seems like a clear win. Is it general
enough to solve our problems?
--
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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