how to detect skew in a column?
- From: Josh Collier <Josh.Collier@xxxxxxxxxxxx>
- To: "Multiple Recipients of List ORACLE-L (E-mail)" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 11 Mar 2004 11:20:02 -0800
Greetings,
I am trying to write some perl to query the database and spit out list of
candidate columns for histograms. I know that dbms_stats has the SKEWONLY
method opt, but that also builds histograms automatically, I don't want to
do that, just want candidates that I can look investigate. I've traced a
dbms_stats session with method opt 'SKEW ONLY', so I think I see how
dbms_stats detects skew, but I'm still investigating.
Any ideas how to identify columns that have skew in them? Besides the
eyeball approach: select count(*),val from table group by val and examine
the result set.
josh
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