Thanks for the reply. There are two things I think I’ve been misunderstood:
1, the point is to do the rewrite without and before catalog access 2, I do want to push the join to the source and equally important pushing the where conditions there Best regards, David 2014.02.13. dátummal, 21:22 időpontban Tom Lane <t...@sss.pgh.pa.us> írta: > David Beck <db...@starschema.net> writes: >> I have table like data structures in the source system for the FDW I work on. >> These tables are sometimes too big and the source system is able to filter >> and join them with limitations, thus it is not optimal to transfer the data >> to Postgres. >> At the same time I want the users to think in terms of the original tables. > >> The idea is to rewrite the SQL queries like this: > >> “SELECT * FROM tableA a, tableB b WHERE a.id=b.id AND a.col1=1234 AND >> b.col2=987” > >> to: > >> “SELECT * FROM fdw_tableA_tableB ab WHERE ab.col1=1234 AND ab.col2=987” > > TBH this sounds like a spectacularly bad idea, especially in the place and > way you propose to do it. You can't even do catalog access safely where > you've put that hook, not to mention that there are many other places > where queries can be submitted. But more generally, an FDW should not > operate in the way you're describing. > > We do lack support for pushing joins to the foreign server, and that needs > to be addressed; but we need to do it in the planner, not by kluging the > query somewhere upstream of that. > > regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
