Re: Plan stability with rule based optimzier
- From: Niall Litchfield <niall.litchfield@xxxxxxxxx>
- To: lex.de.haan@xxxxxxxxxxxxxx
- Date: Fri, 11 Feb 2005 15:06:49 +0000
other groups I can't post to snipped
On Fri, 11 Feb 2005 15:57:39 +0100, Lex de Haan
<lex.de.haan@xxxxxxxxxxxxxx> wrote:
> sorry -- I was trying to say two things at the same time.
> The CHOOSE hint only kicks in CBO if statistics are available,
> because otherwise it would default back to RULE, making the hint useless.
> Therefore I assumed the presence of object statistics.
> So if the intent is to deviate from RULE behavior for a specific SQL
> statement,
> using ALL_ROWS or FIRST_ROWS(n) is the preferred method.
Q1. If RULE is *really* set at the database level (i.e in the
parameter file you have OPTIMIZER_MODE=RULE) is it safe to collect
stats anyway.
Q2. If you can modify the SQL by hinting it, can you modify the SQL?
--
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com
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