Robert Haas <robertmh...@gmail.com> writes: > On Mon, Mar 14, 2016 at 1:04 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> It would be better if we invent an FDW callback that's meant to be >> invoked at this stage, but only call it for FDW(s) actively involved >> in the query. I'm not sure exactly what that ought to look like though. >> Maybe only call the FDW identified as possible owner of the topmost >> scan/join relation?
> I think in the short term that's as well as we're going to do, so +1. > In the long run, I'm interested in making FDWs be able to optimize > queries like foreigntab JOIN localtab ON foreigntab.x = localtab.x > (e.g. by copying localtab to the remote side when it's small); but > that will require revisiting some old decisions, too. Yeah. An alternative definition that would support that would be to call the upper-path-providing callback for each FDW that's responsible for any base relation of the query. But I think that that would often lead to a lot of redundant/wasted computation, and it's not clear to me that we can support such cases without other changes as well. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers