Get rid of the planner's LateralJoinInfo data structure.

I originally modeled this data structure on SpecialJoinInfo, but after
commit acfcd45c 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.

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))
+	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.

src/backend/optimizer/plan/initsplan.c

@@ -47,7 +47,6 @@ typedef struct PostponedQual
 
 static void extract_lateral_references(PlannerInfo *root, RelOptInfo *brel,
 						   Index rtindex);
-static void add_lateral_info(PlannerInfo *root, Relids lhs, Relids rhs);
 static List *deconstruct_recurse(PlannerInfo *root, Node *jtnode,
 					bool below_outer_join,
 					Relids *qualscope, Relids *inner_join_rels,
@@ -382,11 +381,8 @@ extract_lateral_references(PlannerInfo *root, RelOptInfo *brel, Index rtindex)
 
 /*
  * create_lateral_join_info
- *	  For each unflattened LATERAL subquery, create LateralJoinInfo(s) and add
- *	  them to root->lateral_info_list, and fill in the per-rel lateral_relids
- *	  and lateral_referencers sets.  Also generate LateralJoinInfo(s) to
- *	  represent any lateral references within PlaceHolderVars (this part deals
- *	  with the effects of flattened LATERAL subqueries).
+ *	  Fill in the per-base-relation direct_lateral_relids, lateral_relids
+ *	  and lateral_referencers sets.
  *
  * This has to run after deconstruct_jointree, because we need to know the
  * final ph_eval_at values for PlaceHolderVars.
@@ -394,6 +390,7 @@ extract_lateral_references(PlannerInfo *root, RelOptInfo *brel, Index rtindex)
 void
 create_lateral_join_info(PlannerInfo *root)
 {
+	bool		found_laterals = false;
 	Index		rti;
 	ListCell   *lc;
 
@@ -430,8 +427,7 @@ create_lateral_join_info(PlannerInfo *root)
 			{
 				Var		   *var = (Var *) node;
 
-				add_lateral_info(root, bms_make_singleton(var->varno),
-								 brel->relids);
+				found_laterals = true;
 				lateral_relids = bms_add_member(lateral_relids,
 												var->varno);
 			}
@@ -441,7 +437,7 @@ create_lateral_join_info(PlannerInfo *root)
 				PlaceHolderInfo *phinfo = find_placeholder_info(root, phv,
 																false);
 
-				add_lateral_info(root, phinfo->ph_eval_at, brel->relids);
+				found_laterals = true;
 				lateral_relids = bms_add_members(lateral_relids,
 												 phinfo->ph_eval_at);
 			}
@@ -449,69 +445,54 @@ create_lateral_join_info(PlannerInfo *root)
 				Assert(false);
 		}
 
-		/* We now have all the direct lateral refs from this rel */
-		brel->lateral_relids = lateral_relids;
+		/* We now have all the simple lateral refs from this rel */
+		brel->direct_lateral_relids = lateral_relids;
+		brel->lateral_relids = bms_copy(lateral_relids);
 	}
 
 	/*
-	 * Now check for lateral references within PlaceHolderVars, and make
-	 * LateralJoinInfos describing each such reference.  Unlike references in
-	 * unflattened LATERAL RTEs, the referencing location could be a join.
+	 * Now check for lateral references within PlaceHolderVars, and mark their
+	 * eval_at rels as having lateral references to the source rels.
 	 *
-	 * For a PHV that is due to be evaluated at a join, we mark each of the
-	 * join's member baserels as having the PHV's lateral references too. Even
-	 * though the baserels could be scanned without considering those lateral
-	 * refs, we will never be able to form the join except as a path
-	 * parameterized by the lateral refs, so there is no point in considering
-	 * unparameterized paths for the baserels; and we mustn't try to join any
-	 * of those baserels to the lateral refs too soon, either.
+	 * For a PHV that is due to be evaluated at a baserel, mark its source(s)
+	 * as direct lateral dependencies of the baserel (adding onto the ones
+	 * recorded above).  If it's due to be evaluated at a join, mark its
+	 * source(s) as indirect lateral dependencies of each baserel in the join,
+	 * ie put them into lateral_relids but not direct_lateral_relids.  This is
+	 * appropriate because we can't put any such baserel on the outside of a
+	 * join to one of the PHV's lateral dependencies, but on the other hand we
+	 * also can't yet join it directly to the dependency.
 	 */
 	foreach(lc, root->placeholder_list)
 	{
 		PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
 		Relids		eval_at = phinfo->ph_eval_at;
+		int			varno;
 
-		if (phinfo->ph_lateral != NULL)
-		{
-			List	   *vars = pull_var_clause((Node *) phinfo->ph_var->phexpr,
-											   PVC_RECURSE_AGGREGATES,
-											   PVC_INCLUDE_PLACEHOLDERS);
-			ListCell   *lc2;
-			int			ev_at;
-
-			foreach(lc2, vars)
-			{
-				Node	   *node = (Node *) lfirst(lc2);
+		if (phinfo->ph_lateral == NULL)
+			continue;			/* PHV is uninteresting if no lateral refs */
 
-				if (IsA(node, Var))
-				{
-					Var		   *var = (Var *) node;
+		found_laterals = true;
 
-					if (!bms_is_member(var->varno, eval_at))
-						add_lateral_info(root,
-										 bms_make_singleton(var->varno),
-										 eval_at);
-				}
-				else if (IsA(node, PlaceHolderVar))
+		if (bms_get_singleton_member(eval_at, &varno))
 		{
-					PlaceHolderVar *other_phv = (PlaceHolderVar *) node;
-					PlaceHolderInfo *other_phi;
+			/* Evaluation site is a baserel */
+			RelOptInfo *brel = find_base_rel(root, varno);
 
-					other_phi = find_placeholder_info(root, other_phv,
-													  false);
-					if (!bms_is_subset(other_phi->ph_eval_at, eval_at))
-						add_lateral_info(root, other_phi->ph_eval_at, eval_at);
+			brel->direct_lateral_relids =
+				bms_add_members(brel->direct_lateral_relids,
+								phinfo->ph_lateral);
+			brel->lateral_relids =
+				bms_add_members(brel->lateral_relids,
+								phinfo->ph_lateral);
 		}
 		else
-					Assert(false);
-			}
-
-			list_free(vars);
-
-			ev_at = -1;
-			while ((ev_at = bms_next_member(eval_at, ev_at)) >= 0)
 		{
-				RelOptInfo *brel = find_base_rel(root, ev_at);
+			/* Evaluation site is a join */
+			varno = -1;
+			while ((varno = bms_next_member(eval_at, varno)) >= 0)
+			{
+				RelOptInfo *brel = find_base_rel(root, varno);
 
 				brel->lateral_relids = bms_add_members(brel->lateral_relids,
 													   phinfo->ph_lateral);
@@ -519,17 +500,22 @@ create_lateral_join_info(PlannerInfo *root)
 		}
 	}
 
-	/* If we found no lateral references, we're done. */
-	if (root->lateral_info_list == NIL)
+	/*
+	 * If we found no actual lateral references, we're done; but reset the
+	 * hasLateralRTEs flag to avoid useless work later.
+	 */
+	if (!found_laterals)
+	{
+		root->hasLateralRTEs = false;
 		return;
+	}
 
 	/*
-	 * At this point the lateral_relids sets represent only direct lateral
-	 * references.  Replace them by their transitive closure, so that they
-	 * describe both direct and indirect lateral references.  If relation X
-	 * references Y laterally, and Y references Z laterally, then we will have
-	 * to scan X on the inside of a nestloop with Z, so for all intents and
-	 * purposes X is laterally dependent on Z too.
+	 * Calculate the transitive closure of the lateral_relids sets, so that
+	 * they describe both direct and indirect lateral references.  If relation
+	 * X references Y laterally, and Y references Z laterally, then we will
+	 * have to scan X on the inside of a nestloop with Z, so for all intents
+	 * and purposes X is laterally dependent on Z too.
 	 *
 	 * This code is essentially Warshall's algorithm for transitive closure.
 	 * The outer loop considers each baserel, and propagates its lateral
@@ -632,6 +618,8 @@ create_lateral_join_info(PlannerInfo *root)
 					continue;
 				childrel = root->simple_rel_array[appinfo->child_relid];
 				Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
+				Assert(childrel->direct_lateral_relids == NULL);
+				childrel->direct_lateral_relids = brel->direct_lateral_relids;
 				Assert(childrel->lateral_relids == NULL);
 				childrel->lateral_relids = brel->lateral_relids;
 				Assert(childrel->lateral_referencers == NULL);
@@ -641,46 +629,6 @@ create_lateral_join_info(PlannerInfo *root)
 	}
 }
 
-/*
- * add_lateral_info
- *		Add a LateralJoinInfo to root->lateral_info_list, if needed
- *
- * We suppress redundant list entries.  The passed Relids are copied if saved.
- */
-static void
-add_lateral_info(PlannerInfo *root, Relids lhs, Relids rhs)
-{
-	LateralJoinInfo *ljinfo;
-	ListCell   *lc;
-
-	/* Sanity-check the input */
-	Assert(!bms_is_empty(lhs));
-	Assert(!bms_is_empty(rhs));
-	Assert(!bms_overlap(lhs, rhs));
-
-	/*
-	 * The input is redundant if it has the same RHS and an LHS that is a
-	 * subset of an existing entry's.  If an existing entry has the same RHS
-	 * and an LHS that is a subset of the new one, it's redundant, but we
-	 * don't trouble to get rid of it.  The only case that is really worth
-	 * worrying about is identical entries, and we handle that well enough
-	 * with this simple logic.
-	 */
-	foreach(lc, root->lateral_info_list)
-	{
-		ljinfo = (LateralJoinInfo *) lfirst(lc);
-		if (bms_equal(rhs, ljinfo->lateral_rhs) &&
-			bms_is_subset(lhs, ljinfo->lateral_lhs))
-			return;
-	}
-
-	/* Not there, so make a new entry */
-	ljinfo = makeNode(LateralJoinInfo);
-	ljinfo->lateral_lhs = bms_copy(lhs);
-	ljinfo->lateral_rhs = bms_copy(rhs);
-	root->lateral_info_list = lappend(root->lateral_info_list, ljinfo);
-}
-
 
 /*****************************************************************************
  *

src/backend/optimizer/plan/planagg.c

@@ -433,9 +433,8 @@ build_minmax_path(PlannerInfo *root, MinMaxAggInfo *mminfo,
 	subroot->plan_params = NIL;
 	subroot->outer_params = NULL;
 	subroot->init_plans = NIL;
-	/* There shouldn't be any OJ or LATERAL info to translate, as yet */
+	/* There shouldn't be any OJ info to translate, as yet */
 	Assert(subroot->join_info_list == NIL);
-	Assert(subroot->lateral_info_list == NIL);
 	/* and we haven't created PlaceHolderInfos, either */
 	Assert(subroot->placeholder_list == NIL);
 

src/backend/optimizer/plan/planmain.c

@@ -114,7 +114,6 @@ query_planner(PlannerInfo *root, List *tlist,
 	root->right_join_clauses = NIL;
 	root->full_join_clauses = NIL;
 	root->join_info_list = NIL;
-	root->lateral_info_list = NIL;
 	root->placeholder_list = NIL;
 	root->initial_rels = NIL;
 
@@ -201,9 +200,8 @@ query_planner(PlannerInfo *root, List *tlist,
 	add_placeholders_to_base_rels(root);
 
 	/*
-	 * Create the LateralJoinInfo list now that we have finalized
-	 * PlaceHolderVar eval levels and made any necessary additions to the
-	 * lateral_vars lists for lateral references within PlaceHolderVars.
+	 * Construct the lateral reference sets now that we have finalized
+	 * PlaceHolderVar eval levels.
 	 */
 	create_lateral_join_info(root);
 

src/backend/optimizer/plan/planner.c

@@ -1132,9 +1132,8 @@ inheritance_planner(PlannerInfo *root)
 			}
 		}
 
-		/* There shouldn't be any OJ or LATERAL info to translate, as yet */
+		/* There shouldn't be any OJ info to translate, as yet */
 		Assert(subroot.join_info_list == NIL);
-		Assert(subroot.lateral_info_list == NIL);
 		/* and we haven't created PlaceHolderInfos, either */
 		Assert(subroot.placeholder_list == NIL);
 		/* hack to mark target relation as an inheritance partition */

src/backend/optimizer/prep/prepjointree.c

@@ -1150,14 +1150,11 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
 										subroot->append_rel_list);
 
 	/*
-	 * We don't have to do the equivalent bookkeeping for outer-join or
-	 * LATERAL info, because that hasn't been set up yet.  placeholder_list
-	 * likewise.
+	 * We don't have to do the equivalent bookkeeping for outer-join info,
+	 * because that hasn't been set up yet.  placeholder_list likewise.
 	 */
 	Assert(root->join_info_list == NIL);
 	Assert(subroot->join_info_list == NIL);
-	Assert(root->lateral_info_list == NIL);
-	Assert(subroot->lateral_info_list == NIL);
 	Assert(root->placeholder_list == NIL);
 	Assert(subroot->placeholder_list == NIL);
 
@@ -1642,7 +1639,6 @@ pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
 	Assert(root->append_rel_list == NIL);
 	Assert(list_length(parse->rtable) == 1);
 	Assert(root->join_info_list == NIL);
-	Assert(root->lateral_info_list == NIL);
 	Assert(root->placeholder_list == NIL);
 
 	/*
@@ -2839,7 +2835,6 @@ substitute_multiple_relids_walker(Node *node,
 	}
 	/* Shouldn't need to handle planner auxiliary nodes here */
 	Assert(!IsA(node, SpecialJoinInfo));
-	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));

src/backend/optimizer/prep/prepunion.c

@@ -1786,7 +1786,6 @@ adjust_appendrel_attrs_mutator(Node *node,
 	}
 	/* Shouldn't need to handle planner auxiliary nodes here */
 	Assert(!IsA(node, SpecialJoinInfo));
-	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));

src/backend/optimizer/util/placeholder.c

@@ -363,12 +363,10 @@ fix_placeholder_input_needed_levels(PlannerInfo *root)
 
 /*
  * add_placeholders_to_base_rels
- *		Add any required PlaceHolderVars to base rels' targetlists, and
- *		update lateral_vars lists for lateral references contained in them.
+ *		Add any required PlaceHolderVars to base rels' targetlists.
  *
  * If any placeholder can be computed at a base rel and is needed above it,
- * add it to that rel's targetlist, and add any lateral references it requires
- * to the rel's lateral_vars list.  This might look like it could be merged
+ * add it to that rel's targetlist.  This might look like it could be merged
  * with fix_placeholder_input_needed_levels, but it must be separate because
  * join removal happens in between, and can change the ph_eval_at sets.  There
  * is essentially the same logic in add_placeholders_to_joinrel, but we can't
@@ -385,58 +383,22 @@ add_placeholders_to_base_rels(PlannerInfo *root)
 		Relids		eval_at = phinfo->ph_eval_at;
 		int			varno;
 
-		if (bms_get_singleton_member(eval_at, &varno))
+		if (bms_get_singleton_member(eval_at, &varno) &&
+			bms_nonempty_difference(phinfo->ph_needed, eval_at))
 		{
 			RelOptInfo *rel = find_base_rel(root, varno);
 
-			/* add it to reltargetlist if needed above the rel scan level */
-			if (bms_nonempty_difference(phinfo->ph_needed, eval_at))
 			rel->reltargetlist = lappend(rel->reltargetlist,
 										 copyObject(phinfo->ph_var));
-			/* if there are lateral refs in it, add them to lateral_vars */
-			if (phinfo->ph_lateral != NULL)
-			{
-				List	   *vars = pull_var_clause((Node *) phinfo->ph_var->phexpr,
-												   PVC_RECURSE_AGGREGATES,
-												   PVC_INCLUDE_PLACEHOLDERS);
-				ListCell   *lc2;
-
-				foreach(lc2, vars)
-				{
-					Node	   *node = (Node *) lfirst(lc2);
-
-					if (IsA(node, Var))
-					{
-						Var		   *var = (Var *) node;
-
-						if (var->varno != varno)
-							rel->lateral_vars = lappend(rel->lateral_vars,
-														var);
-					}
-					else if (IsA(node, PlaceHolderVar))
-					{
-						PlaceHolderVar *other_phv = (PlaceHolderVar *) node;
-						PlaceHolderInfo *other_phi;
-
-						other_phi = find_placeholder_info(root, other_phv,
-														  false);
-						if (!bms_is_subset(other_phi->ph_eval_at, eval_at))
-							rel->lateral_vars = lappend(rel->lateral_vars,
-														other_phv);
-					}
-					else
-						Assert(false);
-				}
-
-				list_free(vars);
-			}
 		}
 	}
 }
 
 /*
  * add_placeholders_to_joinrel
- *		Add any required PlaceHolderVars to a join rel's targetlist.
+ *		Add any required PlaceHolderVars to a join rel's targetlist;
+ *		and if they contain lateral references, add those references to the
+ *		joinrel's direct_lateral_relids.
  *
  * A join rel should emit a PlaceHolderVar if (a) the PHV is needed above
  * this join level and (b) the PHV can be computed at or below this level.
@@ -463,6 +425,10 @@ add_placeholders_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel)
 				joinrel->reltargetlist = lappend(joinrel->reltargetlist,
 												 phinfo->ph_var);
 				joinrel->width += phinfo->ph_width;
+				/* Adjust joinrel's direct_lateral_relids as needed */
+				joinrel->direct_lateral_relids =
+					bms_add_members(joinrel->direct_lateral_relids,
+									phinfo->ph_lateral);
 			}
 		}
 	}

src/backend/optimizer/util/relnode.c

@@ -111,6 +111,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 	rel->cheapest_total_path = NULL;
 	rel->cheapest_unique_path = NULL;
 	rel->cheapest_parameterized_paths = NIL;
+	rel->direct_lateral_relids = NULL;
 	rel->lateral_relids = NULL;
 	rel->relid = relid;
 	rel->rtekind = rte->rtekind;
@@ -373,6 +374,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->cheapest_total_path = NULL;
 	joinrel->cheapest_unique_path = NULL;
 	joinrel->cheapest_parameterized_paths = NIL;
+	/* init direct_lateral_relids from children; we'll finish it up below */
+	joinrel->direct_lateral_relids =
+		bms_union(outer_rel->direct_lateral_relids,
+				  inner_rel->direct_lateral_relids);
 	joinrel->lateral_relids = min_join_parameterization(root, joinrel->relids,
 														outer_rel, inner_rel);
 	joinrel->relid = 0;			/* indicates not a baserel */
@@ -422,6 +427,18 @@ build_join_rel(PlannerInfo *root,
 	build_joinrel_tlist(root, joinrel, inner_rel);
 	add_placeholders_to_joinrel(root, joinrel);
 
+	/*
+	 * add_placeholders_to_joinrel also took care of adding the ph_lateral
+	 * sets of any PlaceHolderVars computed here to direct_lateral_relids, so
+	 * now we can finish computing that.  This is much like the computation of
+	 * the transitively-closed lateral_relids in min_join_parameterization,
+	 * except that here we *do* have to consider the added PHVs.
+	 */
+	joinrel->direct_lateral_relids =
+		bms_del_members(joinrel->direct_lateral_relids, joinrel->relids);
+	if (bms_is_empty(joinrel->direct_lateral_relids))
+		joinrel->direct_lateral_relids = NULL;
+
 	/*
 	 * Construct restrict and join clause lists for the new joinrel. (The
 	 * caller might or might not need the restrictlist, but I need it anyway

src/backend/optimizer/util/var.c

@@ -782,7 +782,6 @@ flatten_join_alias_vars_mutator(Node *node,
 	Assert(!IsA(node, SubPlan));
 	/* Shouldn't need to handle these planner auxiliary nodes here */
 	Assert(!IsA(node, SpecialJoinInfo));
-	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));
 

src/backend/rewrite/rewriteManip.c

@@ -402,7 +402,6 @@ OffsetVarNodes_walker(Node *node, OffsetVarNodes_context *context)
 	/* Shouldn't need to handle other planner auxiliary nodes here */
 	Assert(!IsA(node, PlanRowMark));
 	Assert(!IsA(node, SpecialJoinInfo));
-	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));
 
@@ -586,7 +585,6 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
 	}
 	/* Shouldn't need to handle other planner auxiliary nodes here */
 	Assert(!IsA(node, SpecialJoinInfo));
-	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));
 
@@ -868,7 +866,6 @@ rangeTableEntry_used_walker(Node *node,
 	Assert(!IsA(node, PlaceHolderVar));
 	Assert(!IsA(node, PlanRowMark));
 	Assert(!IsA(node, SpecialJoinInfo));
-	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));

src/include/nodes/nodes.h

@@ -247,7 +247,6 @@ typedef enum NodeTag
 	T_RestrictInfo,
 	T_PlaceHolderVar,
 	T_SpecialJoinInfo,
-	T_LateralJoinInfo,
 	T_AppendRelInfo,
 	T_PlaceHolderInfo,
 	T_MinMaxAggInfo,

src/include/nodes/relation.h

@@ -226,8 +226,6 @@ typedef struct PlannerInfo
 
 	List	   *join_info_list; /* list of SpecialJoinInfos */
 
-	List	   *lateral_info_list;		/* list of LateralJoinInfos */
-
 	List	   *append_rel_list;	/* list of AppendRelInfos */
 
 	List	   *rowMarks;		/* list of PlanRowMarks */
@@ -357,6 +355,7 @@ typedef struct PlannerInfo
  *			(no duplicates) output from relation; NULL if not yet requested
  *		cheapest_parameterized_paths - best paths for their parameterizations;
  *			always includes cheapest_total_path, even if that's unparameterized
+ *		direct_lateral_relids - rels this rel has direct LATERAL references to
  *		lateral_relids - required outer rels for LATERAL, as a Relids set
  *			(includes both direct and indirect lateral references)
  *
@@ -466,6 +465,7 @@ typedef struct RelOptInfo
 
 	/* parameterization information needed for both base rels and join rels */
 	/* (see also lateral_vars and lateral_referencers) */
+	Relids		direct_lateral_relids;	/* rels directly laterally referenced */
 	Relids		lateral_relids; /* minimum parameterization of rel */
 
 	/* information about a base rel (not set for join rels!) */
@@ -1461,43 +1461,6 @@ typedef struct SpecialJoinInfo
 	List	   *semi_rhs_exprs; /* righthand-side expressions of these ops */
 } SpecialJoinInfo;
 
-/*
- * "Lateral join" info.
- *
- * Lateral references constrain the join order in a way that's somewhat like
- * outer joins, though different in detail.  We construct a LateralJoinInfo
- * for each lateral cross-reference, placing them in the PlannerInfo node's
- * lateral_info_list.
- *
- * For unflattened LATERAL RTEs, we generate LateralJoinInfo(s) in which
- * lateral_rhs is the relid of the LATERAL baserel, and lateral_lhs is a set
- * of relids of baserels it references, all of which must be present on the
- * LHS to compute a parameter needed by the RHS.  Typically, lateral_lhs is
- * a singleton, but it can include multiple rels if the RHS references a
- * PlaceHolderVar with a multi-rel ph_eval_at level.  We disallow joining to
- * only part of the LHS in such cases, since that would result in a join tree
- * with no convenient place to compute the PHV.
- *
- * When an appendrel contains lateral references (eg "LATERAL (SELECT x.col1
- * UNION ALL SELECT y.col2)"), the LateralJoinInfos reference the parent
- * baserel not the member otherrels, since it is the parent relid that is
- * considered for joining purposes.
- *
- * If any LATERAL RTEs were flattened into the parent query, it is possible
- * that the query now contains PlaceHolderVars containing lateral references,
- * representing expressions that need to be evaluated at particular spots in
- * the jointree but contain lateral references to Vars from elsewhere.  These
- * give rise to LateralJoinInfos in which lateral_rhs is the evaluation point
- * of a PlaceHolderVar and lateral_lhs is the set of lateral rels it needs.
- */
-
-typedef struct LateralJoinInfo
-{
-	NodeTag		type;
-	Relids		lateral_lhs;	/* rels needed to compute a lateral value */
-	Relids		lateral_rhs;	/* rel where lateral value is needed */
-} LateralJoinInfo;
-
 /*
  * Append-relation info.
  *