Get rid of the planner's LateralJoinInfo data structure.

I originally modeled this data structure on SpecialJoinInfo, but after
commit acfcd45 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.

Author: tglsfdc

src/backend/nodes/copyfuncs.c

@@ -2066,20 +2066,6 @@ _copySpecialJoinInfo(const SpecialJoinInfo *from)
 	return newnode;
 }
 
-/*
- * _copyLateralJoinInfo
- */
-static LateralJoinInfo *
-_copyLateralJoinInfo(const LateralJoinInfo *from)
-{
-	LateralJoinInfo *newnode = makeNode(LateralJoinInfo);
-
-	COPY_BITMAPSET_FIELD(lateral_lhs);
-	COPY_BITMAPSET_FIELD(lateral_rhs);
-
-	return newnode;
-}
-
 /*
  * _copyAppendRelInfo
  */
@@ -4519,9 +4505,6 @@ copyObject(const void *from)
 		case T_SpecialJoinInfo:
 			retval = _copySpecialJoinInfo(from);
 			break;
-		case T_LateralJoinInfo:
-			retval = _copyLateralJoinInfo(from);
-			break;
 		case T_AppendRelInfo:
 			retval = _copyAppendRelInfo(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -845,15 +845,6 @@ _equalSpecialJoinInfo(const SpecialJoinInfo *a, const SpecialJoinInfo *b)
 	return true;
 }
 
-static bool
-_equalLateralJoinInfo(const LateralJoinInfo *a, const LateralJoinInfo *b)
-{
-	COMPARE_BITMAPSET_FIELD(lateral_lhs);
-	COMPARE_BITMAPSET_FIELD(lateral_rhs);
-
-	return true;
-}
-
 static bool
 _equalAppendRelInfo(const AppendRelInfo *a, const AppendRelInfo *b)
 {
@@ -2860,9 +2851,6 @@ equal(const void *a, const void *b)
 		case T_SpecialJoinInfo:
 			retval = _equalSpecialJoinInfo(a, b);
 			break;
-		case T_LateralJoinInfo:
-			retval = _equalLateralJoinInfo(a, b);
-			break;
 		case T_AppendRelInfo:
 			retval = _equalAppendRelInfo(a, b);
 			break;

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);
@@ -2056,15 +2056,6 @@ _outSpecialJoinInfo(StringInfo str, const SpecialJoinInfo *node)
 	WRITE_NODE_FIELD(semi_rhs_exprs);
 }
 
-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)
 {
@@ -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;

src/backend/optimizer/path/joinrels.c

@@ -231,7 +231,7 @@ join_search_one_level(PlannerInfo *root, int level)
 		 */
 		if (joinrels[level] == NIL &&
 			root->join_info_list == NIL &&
-			root->lateral_info_list == NIL)
+			!root->hasLateralRTEs)
 			elog(ERROR, "failed to build any %d-way joins", level);
 	}
 }
@@ -559,15 +559,7 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
 				 match_sjinfo->jointype == JOIN_FULL))
 				return false;	/* not implementable as nestloop */
 			/* check there is a direct reference from rel2 to rel1 */
-			foreach(l, root->lateral_info_list)
-			{
-				LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(l);
-
-				if (bms_is_subset(ljinfo->lateral_rhs, rel2->relids) &&
-					bms_is_subset(ljinfo->lateral_lhs, rel1->relids))
-					break;
-			}
-			if (l == NULL)
+			if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids))
 				return false;	/* only indirect refs, so reject */
 			/* check we won't have a dangerous PHV */
 			if (have_dangerous_phv(root, rel1->relids, rel2->lateral_relids))
@@ -582,15 +574,7 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
 				 match_sjinfo->jointype == JOIN_FULL))
 				return false;	/* not implementable as nestloop */
 			/* check there is a direct reference from rel1 to rel2 */
-			foreach(l, root->lateral_info_list)
-			{
-				LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(l);
-
-				if (bms_is_subset(ljinfo->lateral_rhs, rel1->relids) &&
-					bms_is_subset(ljinfo->lateral_lhs, rel2->relids))
-					break;
-			}
-			if (l == NULL)
+			if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids))
 				return false;	/* only indirect refs, so reject */
 			/* check we won't have a dangerous PHV */
 			if (have_dangerous_phv(root, rel2->relids, rel1->lateral_relids))
@@ -922,17 +906,9 @@ have_join_order_restriction(PlannerInfo *root,
 	 * If either side has a direct lateral reference to the other, attempt the
 	 * join regardless of outer-join considerations.
 	 */
-	foreach(l, root->lateral_info_list)
-	{
-		LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(l);
-
-		if (bms_is_subset(ljinfo->lateral_rhs, rel2->relids) &&
-			bms_overlap(ljinfo->lateral_lhs, rel1->relids))
-			return true;
-		if (bms_is_subset(ljinfo->lateral_rhs, rel1->relids) &&
-			bms_overlap(ljinfo->lateral_lhs, rel2->relids))
-			return true;
-	}
+	if (bms_overlap(rel1->relids, rel2->direct_lateral_relids) ||
+		bms_overlap(rel2->relids, rel1->direct_lateral_relids))
+		return true;
 
 	/*
 	 * Likewise, if both rels are needed to compute some PlaceHolderVar,

src/backend/optimizer/plan/analyzejoins.c

@@ -439,9 +439,6 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
 		sjinfo->syn_righthand = bms_del_member(sjinfo->syn_righthand, relid);
 	}
 
-	/* There shouldn't be any LATERAL info to translate, as yet */
-	Assert(root->lateral_info_list == NIL);
-
 	/*
 	 * Likewise remove references from PlaceHolderVar data structures,
 	 * removing any no-longer-needed placeholders entirely.