Fix incorrect handling of join clauses pushed into parameterized paths.

In some cases a clause attached to an outer join can be pushed down into
the outer join's RHS even though the clause is not degenerate --- this
can happen if we choose to make a parameterized path for the RHS.  If
the clause ends up attached to a lower outer join, we'd misclassify it
as being a "join filter" not a plain "filter" condition at that node,
leading to wrong query results.

To fix, teach extract_actual_join_clauses to examine each join clause's
required_relids, not just its is_pushed_down flag.  (The latter now
seems vestigial, or at least in need of rethinking, but we won't do
anything so invasive as redefining it in a bug-fix patch.)

This has been wrong since we introduced parameterized paths in 9.2,
though it's evidently hard to hit given the lack of previous reports.
The test case used here involves a lateral function call, and I think
that a lateral reference may be required to get the planner to select
a broken plan; though I wouldn't swear to that.  In any case, even if
LATERAL is needed to trigger the bug, it still affects all supported
branches, so back-patch to all.

Per report from Andreas Karlsson.  Thanks to Andrew Gierth for
preliminary investigation.

Discussion: https://postgr.es/m/f8128b11-c5bf-3539-48cd-234178b2314d@proxel.se

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 5e82a315bf526c23dc52e2a4a13d9a120fdaa170..0e33524117e49255120ae0fd37410985c59c6e29 100644 (file)
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -2062,6 +2062,7 @@ create_nestloop_plan(PlannerInfo *root,
    if (IS_OUTER_JOIN(best_path->jointype))
    {
        extract_actual_join_clauses(joinrestrictclauses,
+                                   best_path->path.parent->relids,
                                    &joinclauses, &otherclauses);
    }
    else
@@ -2162,6 +2163,7 @@ create_mergejoin_plan(PlannerInfo *root,
    if (IS_OUTER_JOIN(best_path->jpath.jointype))
    {
        extract_actual_join_clauses(joinclauses,
+                                   best_path->jpath.path.parent->relids,
                                    &joinclauses, &otherclauses);
    }
    else
@@ -2445,6 +2447,7 @@ create_hashjoin_plan(PlannerInfo *root,
    if (IS_OUTER_JOIN(best_path->jpath.jointype))
    {
        extract_actual_join_clauses(joinclauses,
+                                   best_path->jpath.path.parent->relids,
                                    &joinclauses, &otherclauses);
    }
    else

diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index e394dc2abaec9413d55e3b53165f26189346ee0f..d778c1dd2a01fbfae4e77611f0796206abd4c6d8 100644 (file)
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -418,6 +418,7 @@ extract_actual_clauses(List *restrictinfo_list,
  */
 void
 extract_actual_join_clauses(List *restrictinfo_list,
+                           Relids joinrelids,
                            List **joinquals,
                            List **otherquals)
 {
@@ -432,7 +433,15 @@ extract_actual_join_clauses(List *restrictinfo_list,
 
        Assert(IsA(rinfo, RestrictInfo));
 
-       if (rinfo->is_pushed_down)
+       /*
+        * We must check both is_pushed_down and required_relids, since an
+        * outer-join clause that's been pushed down to some lower join level
+        * via path parameterization will not be marked is_pushed_down;
+        * nonetheless, it must be treated as a filter clause not a join
+        * clause so far as the lower join level is concerned.
+        */
+       if (rinfo->is_pushed_down ||
+           !bms_is_subset(rinfo->required_relids, joinrelids))
        {
            if (!rinfo->pseudoconstant)
                *otherquals = lappend(*otherquals, rinfo->clause);

diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index d404b2a2dc3c62ba2390d32e2e01cf9e77a20672..e6463f0d447f8348c9e98831f396c18e44691b85 100644 (file)
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -36,6 +36,7 @@ extern List *get_all_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
                       bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
+                           Relids joinrelids,
                            List **joinquals,
                            List **otherquals);
 extern bool join_clause_is_movable_to(RestrictInfo *rinfo, RelOptInfo *baserel);

diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index edab441d20f228e877ae1ccc855f6910bed9c40f..a8ddc8bf748adf5cc06f5f1e73e43823d74550fd 100644 (file)
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -3281,6 +3281,33 @@ order by fault;
          | 123 |   122
 (1 row)
 
+explain (costs off)
+select * from
+(values (1, array[10,20]), (2, array[20,30])) as v1(v1x,v1ys)
+left join (values (1, 10), (2, 20)) as v2(v2x,v2y) on v2x = v1x
+left join unnest(v1ys) as u1(u1y) on u1y = v2y;
+                         QUERY PLAN                          
+-------------------------------------------------------------
+ Nested Loop Left Join
+   ->  Values Scan on "*VALUES*"
+   ->  Hash Right Join
+         Hash Cond: (u1.u1y = "*VALUES*_1".column2)
+         Filter: ("*VALUES*_1".column1 = "*VALUES*".column1)
+         ->  Function Scan on unnest u1
+         ->  Hash
+               ->  Values Scan on "*VALUES*_1"
+(8 rows)
+
+select * from
+(values (1, array[10,20]), (2, array[20,30])) as v1(v1x,v1ys)
+left join (values (1, 10), (2, 20)) as v2(v2x,v2y) on v2x = v1x
+left join unnest(v1ys) as u1(u1y) on u1y = v2y;
+ v1x |  v1ys   | v2x | v2y | u1y 
+-----+---------+-----+-----+-----
+   1 | {10,20} |   1 |  10 |  10
+   2 | {20,30} |   2 |  20 |  20
+(2 rows)
+
 --
 -- test handling of potential equivalence clauses above outer joins
 --

diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index e9ec0e29e4263fac3c0ab6f8e4a294ffab635f19..3e5dbe049b7b18a5ce51a8a4c1f2550a3ee3f3b6 100644 (file)
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -987,6 +987,17 @@ select * from
 where fault = 122
 order by fault;
 
+explain (costs off)
+select * from
+(values (1, array[10,20]), (2, array[20,30])) as v1(v1x,v1ys)
+left join (values (1, 10), (2, 20)) as v2(v2x,v2y) on v2x = v1x
+left join unnest(v1ys) as u1(u1y) on u1y = v2y;
+
+select * from
+(values (1, array[10,20]), (2, array[20,30])) as v1(v1x,v1ys)
+left join (values (1, 10), (2, 20)) as v2(v2x,v2y) on v2x = v1x
+left join unnest(v1ys) as u1(u1y) on u1y = v2y;
+
 --
 -- test handling of potential equivalence clauses above outer joins
 --