Re: optimizer_mode = choose ??

From: <gch_at_logibec.com>
Date: Wed, 5 Oct 1994 18:33:32 GMT
Message-ID: <1994Oct5.183332.19018_at_logibec.com>


In article <k1JJTc4w165w_at_vllyoak.resun.com> jp_at_vllyoak.resun.com (Jeff Perry) writes:
> The V7 Oracle Admin manual indicates two possible settings for the
> OPTIMIZER_MODE parameter: RULE & COST. Our databases don't have
> this parameter specifically set, and a query of the v$sysstat view
> indicates optimizer_mode = CHOOSE. What kind of optimization takes
> place with such a setting? It *appears* to default to COST if any
> statistics are available. This is relative to version 7.0.13.1.
> --
> Jeff Perry
> jp_at_vllyoak.resun.com

You're right. If there are statistics available for any one table mentioned in your query the COST mode will be chosen; if not, then the RULE mode will be used.

Gilles Champagne
gch_at_logibec.com Received on Wed Oct 05 1994 - 19:33:32 CET

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