Re: Updates with correlated subqueries slow after 9.2->10.2 upgrade
- From: Neil Kodner <nkodner@xxxxxxxxx>
- To: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx>
- Date: Tue, 17 Nov 2009 15:28:46 -0700
I'm using
estimate_percent=>100 and method_opt=>'FOR ALL COLUMNS SIZE 1' for these
tables
On Tue, Nov 17, 2009 at 3:27 PM, Greg Rahn <greg@xxxxxxxxxxxxxxxxxx> wrote:
> First, are the cardinality estimates representative?
> See "Using GATHER_PLAN_STATISTICS With DBMS_XPLAN.DISPLAY_CURSOR"
> http://structureddata.org/2007/11/21/troubleshooting-bad-execution-plans/
>
> If the cardinality estimates are off by a significant factor, then
> validate your statistics. This may require a higher sample size than
> what is currently used.
>
> There is no use in mucking with parameters/hints until the stats are
> representative.
>
> On Tue, Nov 17, 2009 at 2:02 PM, Neil Kodner <nkodner@xxxxxxxxx> wrote:
> > Once our environment was upgraded from 9.2.0.4 to 10.2.0.4, everything
> > seemed ok except for UPDATE statements that contain correlated select
> > statements. Across the board, we received poor performance compared to
> > running them in 9.2.
>
> --
> Regards,
> Greg Rahn
> http://structureddata.org
>
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