diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index f38da5d0dca0d400bc3dc01b1f57a37e6aae0484..c91f3a55f7a22ea11e1a5457b56ba67d977dd10b 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -731,7 +731,9 @@ build_tlist_to_deparse(RelOptInfo *foreignrel)
* We require columns specified in foreignrel->reltarget->exprs and those
* required for evaluating the local conditions.
*/
- tlist = add_to_flat_tlist(tlist, foreignrel->reltarget->exprs);
+ tlist = add_to_flat_tlist(tlist,
+ pull_var_clause((Node *) foreignrel->reltarget->exprs,
+ PVC_RECURSE_PLACEHOLDERS));
tlist = add_to_flat_tlist(tlist,
pull_var_clause((Node *) fpinfo->local_conds,
PVC_RECURSE_PLACEHOLDERS));
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 1de0bc4796c20a7d686d5ff95943a59d72772fd0..73900d99c59b47a45db5eb40590167cd61ecfe5a 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -2202,6 +2202,64 @@ 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)
+-- non-Var items in targelist of the nullable rel of a join preventing
+-- push-down in some cases
+-- unable to push {ft1, ft2}
+EXPLAIN (COSTS false, VERBOSE)
+SELECT q.a, ft2.c1 FROM (SELECT 13 FROM ft1 WHERE c1 = 13) q(a) 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 FROM ft1 WHERE c1 = 13) q(a) 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)
+
+-- ok to push {ft1, ft2} but not {ft1, ft2, ft4}
+EXPLAIN (COSTS false, VERBOSE)
+SELECT ft4.c1, q.* FROM ft4 LEFT JOIN (SELECT 13, ft1.c1, ft2.c1 FROM ft1 RIGHT JOIN ft2 ON (ft1.c1 = ft2.c1) WHERE ft1.c1 = 12) q(a, b, c) ON (ft4.c1 = q.b) WHERE ft4.c1 BETWEEN 10 AND 15;
+ QUERY PLAN
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Nested Loop Left Join
+ Output: ft4.c1, (13), ft1.c1, ft2.c1
+ Join Filter: (ft4.c1 = ft1.c1)
+ -> Foreign Scan on public.ft4
+ Output: ft4.c1, ft4.c2, ft4.c3
+ Remote SQL: SELECT c1 FROM "S 1"."T 3" WHERE ((c1 >= 10)) AND ((c1 <= 15))
+ -> Materialize
+ Output: ft1.c1, ft2.c1, (13)
+ -> Foreign Scan
+ Output: ft1.c1, ft2.c1, 13
+ Relations: (public.ft1) INNER JOIN (public.ft2)
+ Remote SQL: SELECT r4."C 1", r5."C 1" FROM ("S 1"."T 1" r4 INNER JOIN "S 1"."T 1" r5 ON (((r5."C 1" = 12)) AND ((r4."C 1" = 12)))) ORDER BY r4."C 1" ASC NULLS LAST
+(12 rows)
+
+SELECT ft4.c1, q.* FROM ft4 LEFT JOIN (SELECT 13, ft1.c1, ft2.c1 FROM ft1 RIGHT JOIN ft2 ON (ft1.c1 = ft2.c1) WHERE ft1.c1 = 12) q(a, b, c) ON (ft4.c1 = q.b) WHERE ft4.c1 BETWEEN 10 AND 15;
+ c1 | a | b | c
+----+----+----+----
+ 10 | | |
+ 12 | 13 | 12 | 12
+ 14 | | |
+(3 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 4e31b8e40dd0db323d61636319b66ab6d0776094..4b6ec14c65b795725518d4eb3fa2dfe5accfa343 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -3952,14 +3952,6 @@ postgresImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid)
* 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 join conditions are safe to push down
- * 4) No relation has local filter (this can be relaxed for INNER JOIN, if we
- * can move unpushable clauses upwards in the join tree).
*/
static bool
foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
@@ -4036,6 +4028,26 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
return false;
}
+ /*
+ * deparseExplicitTargetList() isn't smart enough to handle anything other
+ * than a Var. In particular, if there's some PlaceHolderVar that would
+ * need to be evaluated within this join tree (because there's an upper
+ * reference to a quantity that may go to NULL as a result of an outer
+ * join), then we can't try to push the join down because we'll fail when
+ * we get to deparseExplicitTargetList(). However, a PlaceHolderVar that
+ * needs to be evaluated *at the top* of this join tree is OK, because we
+ * can do that locally after fetching the results from the remote side.
+ */
+ foreach(lc, root->placeholder_list)
+ {
+ PlaceHolderInfo *phinfo = lfirst(lc);
+ Relids relids = joinrel->relids;
+
+ if (bms_is_subset(phinfo->ph_eval_at, relids) &&
+ bms_nonempty_difference(relids, phinfo->ph_eval_at))
+ return false;
+ }
+
/* Save the join clauses, for later use. */
fpinfo->joinclauses = joinclauses;
@@ -4116,9 +4128,9 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
}
/*
- * For an inner join, as explained above all restrictions can be treated
- * alike. Treating the pushed down conditions as join conditions allows a
- * top level full outer join to be deparsed without requiring subqueries.
+ * For an inner join, all restrictions can be treated alike. Treating the
+ * pushed down conditions as join conditions allows a top level full outer
+ * join to be deparsed without requiring subqueries.
*/
if (jointype == JOIN_INNER)
{
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 6c2b08c37a4a754957efae97f51b807a41b2df22..a2b03a1a715d99c151f9e1d2ec5e1eea1bdf213a 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -527,6 +527,18 @@ 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);
+-- non-Var items in targelist of the nullable rel of a join preventing
+-- push-down in some cases
+-- unable to push {ft1, ft2}
+EXPLAIN (COSTS false, VERBOSE)
+SELECT q.a, ft2.c1 FROM (SELECT 13 FROM ft1 WHERE c1 = 13) q(a) RIGHT JOIN ft2 ON (q.a = ft2.c1) WHERE ft2.c1 BETWEEN 10 AND 15;
+SELECT q.a, ft2.c1 FROM (SELECT 13 FROM ft1 WHERE c1 = 13) q(a) RIGHT JOIN ft2 ON (q.a = ft2.c1) WHERE ft2.c1 BETWEEN 10 AND 15;
+
+-- ok to push {ft1, ft2} but not {ft1, ft2, ft4}
+EXPLAIN (COSTS false, VERBOSE)
+SELECT ft4.c1, q.* FROM ft4 LEFT JOIN (SELECT 13, ft1.c1, ft2.c1 FROM ft1 RIGHT JOIN ft2 ON (ft1.c1 = ft2.c1) WHERE ft1.c1 = 12) q(a, b, c) ON (ft4.c1 = q.b) WHERE ft4.c1 BETWEEN 10 AND 15;
+SELECT ft4.c1, q.* FROM ft4 LEFT JOIN (SELECT 13, ft1.c1, ft2.c1 FROM ft1 RIGHT JOIN ft2 ON (ft1.c1 = ft2.c1) WHERE ft1.c1 = 12) q(a, b, c) ON (ft4.c1 = q.b) WHERE ft4.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;