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

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: taral(at)mail(dot)utexas(dot)edu (Taral)
Cc: hackers(at)postgreSQL(dot)org
Subject: Re: [GENERAL] Long update query ? (also Re: [GENERAL] CNF vs. DNF)
Date: 1998-10-02 16:40:56
Message-ID: 199810021640.MAA10925@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
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> > This is interesting.  Check CNF size and DNF size.  Choose smallest. 
> > CNF uses existing code, DNF converts to UNIONs.  How do you return the
> > proper rows with/without proper duplicates?
> 
> Create a temporary oid hash? (for each table selected on, I guess)
> 
> Taral
> 

What I did with indexes was to run the previous OR clause index
restrictions through the qualification code, and make sure it failed,
but I am not sure how that is going to work with a more complex WHERE
clause.  Perhaps I need to restrict this to just simple cases of
constants, which are easy to pick out an run through.  Doing this with
joins would be very hard, I think.

-- 
  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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