Hello 2013/8/5 David Gudeman <dave.gude...@gmail.com>: > For those who don't want to go to the link to see what I'm talking > about with query rewrites, I thought I'd give a brief description. > Foreign data wrappers currently do all of their work in the planning > phase but I claim that isn't the right place to optimize foreign > queries with aggregates and GROUP BY because optimizing those things > would involve collapsing multiple plan node back into a single node > for a foreign call. I propose to do these optimizations as query > rewrites instead. So for example suppose t is a foreign table on the > foreign server named fs. Then the query > > SELECT count(*) FROM t > > is rewritten to > > SELECT count FROM fs('select count(*) from t') fs(count bigint) > > where ts() is the pass-through query function for the server fs. To > implement this optimization as a query rewrite, all of the elements of > the result have to be real source-language constructs so the > pass-through query has to be available in Postgresql SQL. >
why you introduce new API? There is still dblink. Regards Pavel > My current implementation of this uses a plugin that hooks into > planner_hook, but I'm hoping that I can get some support for adding > the query rewriting as callback functions for the FDW system. > > Regards, > David Gudeman > http://unobtainabol.blogspot.com > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers