On Mon, 2009-07-13 at 13:33 -0400, Tom Lane wrote: > Simon Riggs <si...@2ndquadrant.com> writes: > > In some cases, we have SQL being submitted that has superfluous > > self-joins. An example would be > > > select count(*) > > from foo1 a, foo1 b > > where a.c1 = b.c1 /* PK join */ > > and a.c2 = 5 > > and b.c2 = 10; > > > You may well ask who would be stupid enough to write SQL like that. The > > answer is of course that it is automatically generated by an ORM. > > Seems like the right answer is "fix the damn ORM". It's hard to believe > this sort of case comes up often enough to justify the cycles that would > be expended (on *every* join query) to try to recognize it.
Yeh, damn ORMs seem to spring up faster than vines. Not just because of this but I wonder if we might benefit from an optimizer setting specifically aimed at the foolishnesses of automatically generated SQL. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
