Re: [SQL] New Optimizer Behaviour In 7.0b1

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Mark Kirkwood <markir(at)ihug(dot)co(dot)nz>
Cc: pgsql-sql(at)postgreSQL(dot)org
Subject: Re: [SQL] New Optimizer Behaviour In 7.0b1
Date: 2000-02-26 23:14:49
Message-ID: 15360.951606889@sss.pgh.pa.us
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Mark Kirkwood <markir(at)ihug(dot)co(dot)nz> writes:
> It looks like the estimate on the big table ( fact1 ) are right order of
> magnitude, but the small table ( dim0 ) ones are too high (and presumably )
> throwing the rest off

At least part of the problem is that the selectivity code doesn't know
how to deal with date/time datatypes :-(. I was waiting for Thomas to
commit the great date/time reorganization before I wrote that code.
But he's done now, so I've gone in and fixed convert_to_scalar to know
about all the surviving date/time types.

If you like, you can pick up the updated version of
src/backend/utils/adt/selfuncs.c from the CVS server, or grab a
snapshot tarball dated later than this message, and see whether
the selectivity estimates get any better.

regards, tom lane

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