On Mon, Mar 14, 2016 at 9:05 AM, Etsuro Fujita <fujita.ets...@lab.ntt.co.jp> wrote:
> Hi, > > Here is the comments for foreign_join_ok in postgres_fdw.c: > > /* > * Assess whether the join between inner and outer relations can be > pushed down > * to the foreign server. As a side effect, save information we obtain > in this > * function to PgFdwRelationInfo passed in. > * > * Joins that satisfy conditions below are safe to push down. > * > * 1) Join type is INNER or OUTER (one of LEFT/RIGHT/FULL) > * 2) Both outer and inner portions are safe to push-down > * 3) All foreign tables in the join belong to the same foreign server > and use > * the same user mapping. > * 4) All join conditions are safe to push down > * 5) No relation has local filter (this can be relaxed for INNER JOIN, > if we > * can move unpushable clauses upwards in the join tree). > */ > > The condition 3 is now checked by the core, so I'd like to remove that > condition from the above comments. > It was left there intentionally to document all the conditions in one place (some from the core and some from the FDW itself), for a ready reference. In case tomorrow core thinks that matching user mapping is not required, postgres_fdw would still require it to be incorporated. > > In addition, I'd like to update some related comments in > src/include/nodes/relation.h and src/backend/optimizer/path/joinpath.c. > Those look fine. Sorry for missing those in the commit and thanks for providing a patch for the same. -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company
