On Tue, Nov 20, 2012 at 02:24:01PM -0600, Merlin Moncure wrote: > On Tue, Nov 20, 2012 at 1:53 PM, Jon Nelson <jnelson+pgsql@xxxxxxxxxxx> wrote: > > As can be seen by the current conversation, not everyone is convinced > that CTEs ought to be an explicit optimization barrier > > On Tue, Nov 20, 2012 at 1:26 PM, Claudio Freire <klaussfreire@xxxxxxxxx> wrote: > > It *could* just be a lack of imagination on my part. But if it were > > not, then it'd be nice for it to be done automatically (since this > > particular CTE behavior bites enough people already). > > Sure. I just find it personally hard to find a good demarcation line > between A: "queries where pushing quals through are universally > beneficial and wanted" and B: "queries where we are inserting an > explicit materialization step to avoid planner issues", particularly > where there is substantial overlap with between A and C: "queries that > are written with a CTE and arguably shouldn't be". > > Put another way, I find CTE to express: 'this then that' where joins > express 'this with that'. So current behavior is not surprising at > all. All that said, there could be a narrow class of low hanging cases > (such as the OP's) that could be sniped...I'm just skeptical. Is thi -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
