On Dec12, 2013, at 19:29 , Tom Lane <t...@sss.pgh.pa.us> wrote: > However ... where this thread started was not about trying to reduce > the remaining statistical imperfections in our existing sampling method. > It was about whether we could reduce the number of pages read for an > acceptable cost in increased statistical imperfection.
True, but Jeff's case shows that even the imperfections of the current sampling method are larger than what the n_distinct estimator expects. Making it even more biased will thus require us to rethink how we obtain a n_distinct estimate or something equivalent. I don't mean that as an argument against changing the sampling method, just as something to watch out for. best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers