Re: Better cardinality estimate when dialing optimizer_features_enable back
Date: Tue, 24 Nov 2009 15:52:51 -0500
The 10053 with the default parameters (ofe 10.2.0.4) can be found at http://www.neilkodner.com/10053_default.txt
The 10053 with the altered session (ofe 10.1.0) is at http://www.neilkodner.com/10053_10_1_0.txt
On Tue, Nov 24, 2009 at 3:32 PM, Greg Rahn <greg_at_structureddata.org> wrote:
> Can you put up 10053 traces from
> select * from letter_bin, where prty_id=102985
> one with the default OFE, and one with 10.1 or 9.2?
> On Tue, Nov 24, 2009 at 11:33 AM, Neil Kodner <nkodner_at_gmail.com> wrote:
> > If I simply select * from letter_bin, where prty_id=102985 with all
> > session parameters, I get cardinatlity of 12, which is the number of not
> > null values / NDV.
> > If I change OFE to 10.1.0 or 9.2.0, I get a correct value for
> > On Tue, Nov 24, 2009 at 2:28 PM, Greg Rahn <greg_at_structureddata.org>
> >> So then it appears the predicate ("LETTER_BIN"."PRTY_ID"=102985) via
> >> LETTER_BIN_PRTY_ID_I is row source with the issue. In the first query
> >> it looks to be off by 2 orders of magnitude, 1692 vs 14, Thats
> >> usually not so good in an NL plan.
> >> Are the stats on the table and index both using 100% sample?
> >> Is there a histogram on LETTER_BIN. PRTY_ID?
> >> If you switch OFE to 9.2 just for the test query, do you get a
> >> different cardinality estimate, or is it that OFE=9.2 just yields an
> >> overall better plan for the full query?
> >> On Tue, Nov 24, 2009 at 11:19 AM, Neil Kodner <nkodner_at_gmail.com>
> >> > For what its worth, if I just explain plan on select * from letter_bin
> >> > where
> >> > prty_id=12345, I get an incorrect cardinality estimate. For that
> >> > reason, I
> >> > have not tried isolating other fields.
> >> --
> >> Regards,
> >> Greg Rahn
> >> http://structureddata.org
> Greg Rahn