Get rid of the planner's LateralJoinInfo data structure.

I originally modeled this data structure on SpecialJoinInfo, but after
commit acfcd45cacb6df23 that looks like a pretty poor decision.
All we really need is relid sets identifying laterally-referenced rels;
and most of the time, what we want to know about includes indirect lateral
references, a case the LateralJoinInfo data was unsuited to compute with
any efficiency.  The previous commit redefined RelOptInfo.lateral_relids
as the transitive closure of lateral references, so that it easily supports
checking indirect references.  For the places where we really do want just
direct references, add a new RelOptInfo field direct_lateral_relids, which
is easily set up as a copy of lateral_relids before we perform the
transitive closure calculation.  Then we can just drop lateral_info_list
and LateralJoinInfo and the supporting code.  This makes the planner's
handling of lateral references noticeably more efficient, and shorter too.

Such a change can't be back-patched into stable branches for fear of
breaking extensions that might be looking at the planner's data structures;
but it seems not too late to push it into 9.5, so I've done so.

1 files changed, 1 insertions, 13 deletions

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index f07c7933b14..63fae82aba0 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1847,7 +1847,6 @@ _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);
@@ -1892,6 +1891,7 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
 	WRITE_NODE_FIELD(cheapest_total_path);
 	WRITE_NODE_FIELD(cheapest_unique_path);
 	WRITE_NODE_FIELD(cheapest_parameterized_paths);
+	WRITE_BITMAPSET_FIELD(direct_lateral_relids);
 	WRITE_BITMAPSET_FIELD(lateral_relids);
 	WRITE_UINT_FIELD(relid);
 	WRITE_OID_FIELD(reltablespace);
@@ -2057,15 +2057,6 @@ _outSpecialJoinInfo(StringInfo str, const SpecialJoinInfo *node)
 }
 
 static void
-_outLateralJoinInfo(StringInfo str, const LateralJoinInfo *node)
-{
-	WRITE_NODE_TYPE("LATERALJOININFO");
-
-	WRITE_BITMAPSET_FIELD(lateral_lhs);
-	WRITE_BITMAPSET_FIELD(lateral_rhs);
-}
-
-static void
 _outAppendRelInfo(StringInfo str, const AppendRelInfo *node)
 {
 	WRITE_NODE_TYPE("APPENDRELINFO");
@@ -3355,9 +3346,6 @@ _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;