Chris Mayfield <cmayfiel@xxxxxxxxxxxxx> writes: >>> So the long and the short of it is that the COALESCE acts as an >>> optimization fence in the presence of outer joins. We've seen this >>> before and there are some rough ideas about fixing it. > You may already have this rough idea somewhere, but it seems to me that > the view could be flattened into the upper query as long as the join > predicates don't depend on coalesced columns. In the examples I sent, > even if the COALESCE is evaluated at the very end of the query, the > merge join (on the id columns) would still be correct. But the output would not be: the join column would fail to go to null when it was supposed to. See the example that made us put in that restriction in the first place: http://archives.postgresql.org/pgsql-bugs/2001-04/msg00223.php regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
