From: Sbragion Denis <infotecn@tin.it>
To: David Hartwig <daybee@bellatlantic.net>
To: Bruce Momjian <maillist@candle.pha.pa.us>
Cc: hannu@trust.ee
Cc: pgsql-interfaces@postgreSQL.org
Cc: hackers@postgreSQL.org
Subject: Re: [INTERFACES] Re: [HACKERS] changes in 6.4
Date: Mon, 31 Aug 1998 08:53:12 +0200
Message-ID: <3.0.5.32.19980831085312.00986cc0@MBox.InfoTecna.com> (raw)
In-Reply-To: <35E9726E.C6E73049@bellatlantic.net>
References: <199808290344.XAA28089@candle.pha.pa.us>
Hello,
At 11.40 30/08/98 -0400, David Hartwig wrote:
>> Why is the system cnf'ifying the query. Because it wants to have a
>> list of qualifications that are AND'ed, so it can just pick the most
>> restrictive/cheapest, and evaluate that one first.
Just a small question about all this optimizations stuff. I'm not a
database expert but I think we are talking about a NP-complete problem.
Could'nt we convert this optimization problem into another NP one that is
known to have a good solution ? For example for the traveling salesman
problem there's an alghoritm that provide a solution that's never more than
two times the optimal one an provides results that are *really* near the
optimal one most of the times. The simplex alghoritm may be another
example. I think that this kind of alghoritm would be better than a
collection ot tricks for special cases, and this tricks could be used
anyway when special cases are detected. Furthermore I also know that exists
a free program I used in the past that provides this kind of optimizations
for chip design. I don't remember the exact name of the program but I
remember it came from Berkeley university. Of course may be I'm totally
missing the point.
Hope it helps !
Bye!
Dr. Sbragion Denis
InfoTecna
Tel, Fax: +39 39 2324054
URL: http://space.tin.it/internet/dsbragio
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Cc: infotecn@tin.it, daybee@bellatlantic.net, maillist@candle.pha.pa.us, hannu@trust.ee, hackers@postgreSQL.org
Subject: Re: [INTERFACES] Re: [HACKERS] changes in 6.4
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