On Thu, Sep 4, 2014 at 08:37:08AM -0400, Robert Haas wrote: > The main problem I see here is that accurate costing may require a > round-trip to the remote server. If there is only one path that is > probably OK; the cost of asking the question will usually be more than > paid for by hearing that the pushed-down join clobbers the other > possible methods of executing the query. But if there are many paths, > for example because there are multiple sets of useful pathkeys, it > might start to get a bit expensive. > > Probably both the initial cost and final cost calculations should be > delegated to the FDW, but maybe within postgres_fdw, the initial cost > should do only the work that can be done without contacting the remote > server; then, let the final cost step do that if appropriate. But I'm > not entirely sure what is best here.
I am thinking eventually we will need to cache the foreign server statistics on the local server. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
