Στις Friday 21 January 2011 22:22:24 ο/η Tom Lane έγραψε: > "Kevin Grittner" <kevin.gritt...@wicourts.gov> writes: > > Tom Lane <t...@sss.pgh.pa.us> wrote: > >> If it should be less than 1, then what? > > > 1 - (estimated tuples / estimated distinct values) ? > > Uh, no. The number we're after is the probability that an outer tuple > has at least one unequal value in the inner relation. This is not 1 > minus the probability that a *specific* inner value is equal, which is > what I think your formula is estimating.
Isn't this probablity (an outer tuple has at least one unequal value in the inner relation) = 1 - (probability that all values in the inner relation are equal to the value of the outer tuple) Anyways, glad to see smth came out of this. Thx > > regards, tom lane > -- Achilleas Mantzios -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
