On Fri, 2012-03-16 at 18:25 +0000, Simon Riggs wrote: > Any time we apply a LIMIT clause to a plan with a SeqScan or > unqualified IndexScan, we shouldn't assume the scan will do less than > say 10% of the table. It might, but its an unsafe assumption because > as the selectivity decreases so does the safety of the assumption that > rows are uniformly distributed.
Just trying to follow along. You mean "as the selectivity _increases_ the safety of the assumption that the rows are uniformly distributed decreases", right? Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers