Fix up planner infrastructure to support LATERAL properly.

This patch takes care of a number of problems having to do with failure
to choose valid join orders and incorrect handling of lateral references
pulled up from subqueries.  Notable changes:

* Add a LateralJoinInfo data structure similar to SpecialJoinInfo, to
represent join ordering constraints created by lateral references.
(I first considered extending the SpecialJoinInfo structure, but the
semantics are different enough that a separate data structure seems
better.)  Extend join_is_legal() and related functions to prevent trying
to form unworkable joins, and to ensure that we will consider joins that
satisfy lateral references even if the joins would be clauseless.

* Fill in the infrastructure needed for the last few types of relation scan
paths to support parameterization.  We'd have wanted this eventually
anyway, but it is necessary now because a relation that gets pulled up out
of a UNION ALL subquery may acquire a reltargetlist containing lateral
references, meaning that its paths *have* to be parameterized whether or
not we have any code that can push join quals down into the scan.

* Compute data about lateral references early in query_planner(), and save
in RelOptInfo nodes, to avoid repetitive calculations later.

* Assorted corner-case bug fixes.

There's probably still some bugs left, but this is a lot closer to being
real than it was before.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 9dee0414f36..01f381e9bad 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1699,6 +1699,7 @@ _outPlannerInfo(StringInfo str, const PlannerInfo *node)
 	WRITE_NODE_FIELD(right_join_clauses);
 	WRITE_NODE_FIELD(full_join_clauses);
 	WRITE_NODE_FIELD(join_info_list);
+	WRITE_NODE_FIELD(lateral_info_list);
 	WRITE_NODE_FIELD(append_rel_list);
 	WRITE_NODE_FIELD(rowMarks);
 	WRITE_NODE_FIELD(placeholder_list);
@@ -1713,6 +1714,7 @@ _outPlannerInfo(StringInfo str, const PlannerInfo *node)
 	WRITE_FLOAT_FIELD(limit_tuples, "%.0f");
 	WRITE_BOOL_FIELD(hasInheritedTarget);
 	WRITE_BOOL_FIELD(hasJoinRTEs);
+	WRITE_BOOL_FIELD(hasLateralRTEs);
 	WRITE_BOOL_FIELD(hasHavingQual);
 	WRITE_BOOL_FIELD(hasPseudoConstantQuals);
 	WRITE_BOOL_FIELD(hasRecursion);
@@ -1743,6 +1745,8 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
 	WRITE_ENUM_FIELD(rtekind, RTEKind);
 	WRITE_INT_FIELD(min_attr);
 	WRITE_INT_FIELD(max_attr);
+	WRITE_NODE_FIELD(lateral_vars);
+	WRITE_BITMAPSET_FIELD(lateral_relids);
 	WRITE_NODE_FIELD(indexlist);
 	WRITE_UINT_FIELD(pages);
 	WRITE_FLOAT_FIELD(tuples, "%.0f");
@@ -1891,6 +1895,15 @@ _outSpecialJoinInfo(StringInfo str, const SpecialJoinInfo *node)
 }
 
 static void
+_outLateralJoinInfo(StringInfo str, const LateralJoinInfo *node)
+{
+	WRITE_NODE_TYPE("LATERALJOININFO");
+
+	WRITE_UINT_FIELD(lateral_rhs);
+	WRITE_BITMAPSET_FIELD(lateral_lhs);
+}
+
+static void
 _outAppendRelInfo(StringInfo str, const AppendRelInfo *node)
 {
 	WRITE_NODE_TYPE("APPENDRELINFO");
@@ -3036,6 +3049,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_SpecialJoinInfo:
 				_outSpecialJoinInfo(str, obj);
 				break;
+			case T_LateralJoinInfo:
+				_outLateralJoinInfo(str, obj);
+				break;
 			case T_AppendRelInfo:
 				_outAppendRelInfo(str, obj);
 				break;