>> What is the specific difference between what you are talking about and >> what scalarineqsel already implements? > > Hmm... Northing new. Feel sorry for bothering you. I did not realize > histograms are implemented. >
Well, ISTM there is a profound difference. For scalarineqsel we care about the total number of values in a bucket. For eqsel we care about the total number of *distinct* values in each bucket ( which we don't track ). IMHO, the whole idea of increasing mcv's seems a mistake. Why not use the limited storage in pg_statistic to try and estimate the selectivity for ranges of values rather than a single value? That gives way better coverage of the distribution. If the number of values is too high to fit in a single bucket we put it in an mcv slot anyways. *That* should be the mechanism by which the number of mcv's increases. I guess this is a bit off topic for the middle of a commit fest though. -Nathan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers