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September 2009

An interview with Mark Townsend

While attending the 11gR2 launch event in Milan last Thursday, I had the distinguished opportunity (invited, as a blogger, by the Oracle team that was organizing the event) to meet Mark Townsend and exchange a few words about the new features of 11gR2 and the Oracle database in general as well.

For those who don’t know, Mark is (among other things) the Vice President in charge of coordinating the Product Managers and a technical expert at the same time, and this rare combination has the advantage that you can ask him about any feature you like at whatever granularity you like, from the strategic level down to the technical gory details.…

CBO: the “non-empty result set” assumption

The CBO assumes that SELECT statements are always going to retrieve at least one row – even if this is not necessarily the case, of course. Understanding why this is done is both useful and fascinating.

We must start from the very beginning and remember that one of the most important tasks of the CBO is estimating the statement cardinality, that is, to make a guess about the number of rows that will be fetched.…