Fix planner problems with LATERAL references in PlaceHolderVars.

The planner largely failed to consider the possibility that a
PlaceHolderVar's expression might contain a lateral reference to a Var
coming from somewhere outside the PHV's syntactic scope.  We had a previous
report of a problem in this area, which I tried to fix in a quick-hack way
in commit 4da6439bd8553059766011e2a42c6e39df08717f, but Antonin Houska
pointed out that there were still some problems, and investigation turned
up other issues.  This patch largely reverts that commit in favor of a more
thoroughly thought-through solution.  The new theory is that a PHV's
ph_eval_at level cannot be higher than its original syntactic level.  If it
contains lateral references, those don't change the ph_eval_at level, but
rather they create a lateral-reference requirement for the ph_eval_at join
relation.  The code in joinpath.c needs to handle that.

Another issue is that createplan.c wasn't handling nested PlaceHolderVars
properly.

In passing, push knowledge of lateral-reference checks for join clauses
into join_clause_is_movable_to.  This is mainly so that FDWs don't need
to deal with it.

This patch doesn't fix the original join-qual-placement problem reported by
Jeremy Evans (and indeed, one of the new regression test cases shows the
wrong answer because of that).  But the PlaceHolderVar problems need to be
fixed before that issue can be addressed, so committing this separately
seems reasonable.

1 files changed, 13 insertions, 39 deletions

diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 65eb344cde4..606734a1221 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -141,12 +141,10 @@ static void match_restriction_clauses_to_index(RelOptInfo *rel,
 								   IndexClauseSet *clauseset);
 static void match_join_clauses_to_index(PlannerInfo *root,
 							RelOptInfo *rel, IndexOptInfo *index,
-							Relids lateral_referencers,
 							IndexClauseSet *clauseset,
 							List **joinorclauses);
 static void match_eclass_clauses_to_index(PlannerInfo *root,
 							  IndexOptInfo *index,
-							  Relids lateral_referencers,
 							  IndexClauseSet *clauseset);
 static void match_clauses_to_index(IndexOptInfo *index,
 					   List *clauses,
@@ -220,14 +218,14 @@ static Const *string_to_const(const char *str, Oid datatype);
  *
  * Note: check_partial_indexes() must have been run previously for this rel.
  *
- * Note: in corner cases involving LATERAL appendrel children, it's possible
- * that rel->lateral_relids is nonempty.  Currently, we include lateral_relids
- * into the parameterization reported for each path, but don't take it into
- * account otherwise.  The fact that any such rels *must* be available as
- * parameter sources perhaps should influence our choices of index quals ...
- * but for now, it doesn't seem worth troubling over.  In particular, comments
- * below about "unparameterized" paths should be read as meaning
- * "unparameterized so far as the indexquals are concerned".
+ * Note: in cases involving LATERAL references in the relation's tlist, it's
+ * possible that rel->lateral_relids is nonempty.  Currently, we include
+ * lateral_relids into the parameterization reported for each path, but don't
+ * take it into account otherwise.	The fact that any such rels *must* be
+ * available as parameter sources perhaps should influence our choices of
+ * index quals ... but for now, it doesn't seem worth troubling over.
+ * In particular, comments below about "unparameterized" paths should be read
+ * as meaning "unparameterized so far as the indexquals are concerned".
  */
 void
 create_index_paths(PlannerInfo *root, RelOptInfo *rel)
@@ -236,7 +234,6 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
 	List	   *bitindexpaths;
 	List	   *bitjoinpaths;
 	List	   *joinorclauses;
-	Relids		lateral_referencers;
 	IndexClauseSet rclauseset;
 	IndexClauseSet jclauseset;
 	IndexClauseSet eclauseset;
@@ -246,23 +243,6 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
 	if (rel->indexlist == NIL)
 		return;
 
-	/*
-	 * If there are any rels that have LATERAL references to this one, we
-	 * cannot use join quals referencing them as index quals for this one,
-	 * since such rels would have to be on the inside not the outside of a
-	 * nestloop join relative to this one.	Create a Relids set listing all
-	 * such rels, for use in checks of potential join clauses.
-	 */
-	lateral_referencers = NULL;
-	foreach(lc, root->lateral_info_list)
-	{
-		LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(lc);
-
-		if (bms_is_member(rel->relid, ljinfo->lateral_lhs))
-			lateral_referencers = bms_add_member(lateral_referencers,
-												 ljinfo->lateral_rhs);
-	}
-
 	/* Bitmap paths are collected and then dealt with at the end */
 	bitindexpaths = bitjoinpaths = joinorclauses = NIL;
 
@@ -303,7 +283,7 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
 		 * EquivalenceClasses.	Also, collect join OR clauses for later.
 		 */
 		MemSet(&jclauseset, 0, sizeof(jclauseset));
-		match_join_clauses_to_index(root, rel, index, lateral_referencers,
+		match_join_clauses_to_index(root, rel, index,
 									&jclauseset, &joinorclauses);
 
 		/*
@@ -311,7 +291,7 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
 		 * the index.
 		 */
 		MemSet(&eclauseset, 0, sizeof(eclauseset));
-		match_eclass_clauses_to_index(root, index, lateral_referencers,
+		match_eclass_clauses_to_index(root, index,
 									  &eclauseset);
 
 		/*
@@ -1957,7 +1937,6 @@ match_restriction_clauses_to_index(RelOptInfo *rel, IndexOptInfo *index,
 static void
 match_join_clauses_to_index(PlannerInfo *root,
 							RelOptInfo *rel, IndexOptInfo *index,
-							Relids lateral_referencers,
 							IndexClauseSet *clauseset,
 							List **joinorclauses)
 {
@@ -1969,11 +1948,7 @@ match_join_clauses_to_index(PlannerInfo *root,
 		RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
 		/* Check if clause can be moved to this rel */
-		if (!join_clause_is_movable_to(rinfo, rel->relid))
-			continue;
-
-		/* Not useful if it conflicts with any LATERAL references */
-		if (bms_overlap(rinfo->clause_relids, lateral_referencers))
+		if (!join_clause_is_movable_to(rinfo, rel))
 			continue;
 
 		/* Potentially usable, so see if it matches the index or is an OR */
@@ -1991,7 +1966,6 @@ match_join_clauses_to_index(PlannerInfo *root,
  */
 static void
 match_eclass_clauses_to_index(PlannerInfo *root, IndexOptInfo *index,
-							  Relids lateral_referencers,
 							  IndexClauseSet *clauseset)
 {
 	int			indexcol;
@@ -2012,7 +1986,7 @@ match_eclass_clauses_to_index(PlannerInfo *root, IndexOptInfo *index,
 														 index->rel,
 												  ec_member_matches_indexcol,
 														 (void *) &arg,
-														 lateral_referencers);
+											index->rel->lateral_referencers);
 
 		/*
 		 * We have to check whether the results actually do match the index,
@@ -2644,7 +2618,7 @@ check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
 		RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
 		/* Check if clause can be moved to this rel */
-		if (!join_clause_is_movable_to(rinfo, rel->relid))
+		if (!join_clause_is_movable_to(rinfo, rel))
 			continue;
 
 		clauselist = lappend(clauselist, rinfo);