On Wed, Feb 23, 2011 at 10:30 PM, Bruce Momjian <br...@momjian.us> wrote: > 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?
Beats me. What do you have in mind? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers