Dne 17.11.2010 06:58, Tom Lane napsal(a): >> BTW I think the default estimate used to be 1000, so it was changed in >> one of the 8.x releases? Can you point me to the docs? I've even tried >> to find that in the sources, but unsuccessfully. > > It's DEFAULT_RANGE_INEQ_SEL, and AFAIR it hasn't changed in quite a while. > But I wouldn't be surprised if the behavior of this example changed when > we boosted the default statistics target.
I've been thinking about this and I think it might be improved. If I understand the logic corretly, it says 'use half of the histogram bin size'. But the value #define DEFAULT_RANGE_INEQ_SEL 0.005 says it's always 0.5%, which is not not true if STATISTICS TARGET is not 100. This could actually yield 10x more precise estimates when the STATISTICS TARGET is set to 1000. OK, I know the default value is 100, just thinking about how to improve the estimates. Tomas -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
