RE: Join cardinality and query tuning.

  • From: "Charu Joshi" <joshic@xxxxxxxxxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 3 Nov 2004 14:55:45 +0530

That is the problem - I don't have enough permissions to take 10053 trace.
Getting any such trace is a headache. If there is absolutely no other way,
then I will try replicating this on some other environment.

Thanks & regards,

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Wolfgang Breitling
Sent: Wednesday, November 03, 2004 2:49 PM
To: joshic@xxxxxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: Join cardinality and query tuning.

Can you run a 10053 event trace and post the trace? It will show all the
statistics and values the optimizer uses to calculate the join cardinality.
Maybe that will shed some light on the "mystery". I have seen many cases
the CBO's join selectivity calculation is different from the formula you
which you got from my paper and which I got from a metalink note.

Quoting Charu Joshi <joshic@xxxxxxxxxxxxxx>:

> Thanks Lex,
> Then why is the row-source cardinality shown in the Explain Plan radically
> different from the one calculated using this formula (Please refer to my
> original post.)? Is there any silly mistake in my calculations (I quite am
> prone to that.)?


Wolfgang Breitling
Oracle 7,8,8i,9i OCP DBA
Centrex Consulting Corporation



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