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From: mao@eden.Berkeley.EDU (Mike Olson)
Newsgroups: comp.databases
Subject: Re: Query Optimization
Keywords: magic sets
Message-ID: <11262@pasteur.Berkeley.EDU>
Date: 19 Feb 91 17:23:04 GMT
References: <1991Feb14.192012.6084@doe.utoronto.ca> <13511@blia.sharebase.com>
Sender: news@pasteur.Berkeley.EDU
Reply-To: mao@eden.Berkeley.EDU (Mike Olson)
Organization: University of California, Berkeley
Lines: 16

In <13511@blia.sharebase.com>, mike@woodstock.UUCP (Mike Ubell) writes

> ShareBase III (in beta test, scheduled for
> release around June) does a complete optimization search for up to
> about 10 way joins and a pruned search up to 32 way.  As far as I know
> it will generate the same query plan for any semanticly equivalent SQL
> statements.

does this optimizer consider nested subqueries to be semantically equivalent
to their flattened expressions?  do you have to flatten subqueries in order
to make this happen?  this seems kind of tricky.

					mike olson
					postgres research group
					uc berkeley
					mao@postgres.berkeley.edu


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