diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index 1de0bc4..86e9e24 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -2202,6 +2202,37 @@ SELECT t1.c1, t2.c1 FROM (ft5 t1 JOIN v_ft5 t2 ON (t1.c1 = t2.c1)) left join (ft Remote SQL: SELECT c1 FROM "S 1"."T 4" (27 rows) +-- query which introduces placeholders in the targetlist +-- the join should not be pushed down since correct result cannot be ensured +-- without pushing down the subquery which is currently not supported +EXPLAIN (COSTS false, VERBOSE) +SELECT q.a, ft2.c1 FROM (SELECT 13 as a FROM ft1 WHERE c1 = 13) q RIGHT JOIN ft2 ON (q.a = ft2.c1) WHERE ft2.c1 BETWEEN 10 AND 15; + QUERY PLAN +--------------------------------------------------------------------------------------------------------------------------- + Nested Loop Left Join + Output: (13), ft2.c1 + Join Filter: (13 = ft2.c1) + -> Foreign Scan on public.ft2 + Output: ft2.c1 + Remote SQL: SELECT "C 1" FROM "S 1"."T 1" WHERE (("C 1" >= 10)) AND (("C 1" <= 15)) ORDER BY "C 1" ASC NULLS LAST + -> Materialize + Output: (13) + -> Foreign Scan on public.ft1 + Output: 13 + Remote SQL: SELECT NULL FROM "S 1"."T 1" WHERE (("C 1" = 13)) +(11 rows) + +SELECT q.a, ft2.c1 FROM (SELECT 13 as a FROM ft1 WHERE c1 = 13) q RIGHT JOIN ft2 ON (q.a = ft2.c1) WHERE ft2.c1 BETWEEN 10 AND 15; + a | c1 +----+---- + | 10 + | 11 + | 12 + 13 | 13 + | 14 + | 15 +(6 rows) + -- recreate the dropped user mapping for further tests CREATE USER MAPPING FOR CURRENT_USER SERVER loopback; DROP USER MAPPING FOR PUBLIC SERVER loopback; diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 4d17272..ec86b9a 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -4036,6 +4036,20 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, return false; } + /* + * Cannot push down if any PlaceHolderVars in its result are needed above + * the join. + */ + foreach(lc, root->placeholder_list) + { + PlaceHolderInfo *phinfo = lfirst(lc); + Relids relids = joinrel->relids; + + if (bms_nonempty_difference(phinfo->ph_needed, relids) && + bms_is_subset(phinfo->ph_eval_at, relids)) + return false; + } + /* Save the join clauses, for later use. */ fpinfo->joinclauses = joinclauses; diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 6c2b08c..3af48f8 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -527,6 +527,13 @@ EXECUTE join_stmt; EXPLAIN (COSTS false, VERBOSE) SELECT t1.c1, t2.c1 FROM (ft5 t1 JOIN v_ft5 t2 ON (t1.c1 = t2.c1)) left join (ft5 t3 JOIN v_ft5 t4 ON (t3.c1 = t4.c1)) ON (t1.c1 = t3.c1); +-- query which introduces placeholders in the targetlist +-- the join should not be pushed down since correct result cannot be ensured +-- without pushing down the subquery which is currently not supported +EXPLAIN (COSTS false, VERBOSE) +SELECT q.a, ft2.c1 FROM (SELECT 13 as a FROM ft1 WHERE c1 = 13) q RIGHT JOIN ft2 ON (q.a = ft2.c1) WHERE ft2.c1 BETWEEN 10 AND 15; +SELECT q.a, ft2.c1 FROM (SELECT 13 as a FROM ft1 WHERE c1 = 13) q RIGHT JOIN ft2 ON (q.a = ft2.c1) WHERE ft2.c1 BETWEEN 10 AND 15; + -- recreate the dropped user mapping for further tests CREATE USER MAPPING FOR CURRENT_USER SERVER loopback; DROP USER MAPPING FOR PUBLIC SERVER loopback;