Oracle database internals by Riyaj

Discussions about Oracle performance tuning, RAC, Oracle internal & E-business suite.

Archive for December, 2008

Correlation, nocorrelation and extended stats

Posted by Riyaj Shamsudeen on December 19, 2008

I blogged about extended stats in my earlier blog, extended stats, and also documented that as an investigation in Investigations: extended stats and multi-column correlation. I was testing extended stats further and ran in to some interesting situations.

Extended stats can be used to store correlation between columns. Correlation between two columns needs to detect at least, two properties of the column values:

  1. Correlated column values
  2. Uncorrelated column values

Let’s explore this further.
Test case
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Posted in 11g, CBO, Performance tuning | 4 Comments »