On Thu, Dec 12, 2013 at 3:56 PM, Josh Berkus <j...@agliodbs.com> wrote: > > Estimated grouping should, however, affect MCVs. In cases where we > estimate that grouping levels are high, the expected % of observed > values should be "discounted" somehow. That is, with total random > distribution you have a 1:1 ratio between observed frequency of a value > and assumed frequency. However, with highly grouped values, you might > have a 2:1 ratio.
Cross validation can help there. But it's costly. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
