Robert Haas wrote: > If you want to take the above as in any way an exhaustive survey of > the landscape (which it isn't), C seems like a standout, maybe > augmented by the making the planner able to notice that A1 = x1 AND A2 > = x2 is equivalent to (A1,A2) = (x1, x2) so you don't have to rewrite > queries as much. > > I don't really know how to handle the join selectivity problem. I am > not convinced that there is a better solution to that than decorating > the query. After all the join selectivity depends not only on the > join clause itself, but also on what you've filtered out of each table > in the meantime.
Thinking some more, I think another downside to the "decorate the query" idea is that many queries use constants that are supplied only at runtime, so there would be no way to hard-code a selectivity value into a query when you don't know the value. Could a selectivity function handle that? -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
