4 files changed, 129 insertions, 8 deletions

diff --git a/src/backend/executor/nodeNestloop.c b/src/backend/executor/nodeNestloop.c
index e98bc0f5a30..b4793583587 100644
--- a/src/backend/executor/nodeNestloop.c
+++ b/src/backend/executor/nodeNestloop.c
@@ -148,6 +148,7 @@ ExecNestLoop(NestLoopState *node)
 
 				prm = &(econtext->ecxt_param_exec_vals[paramno]);
 				/* Param value should be an OUTER var */
+				Assert(IsA(nlp->paramval, Var));
 				Assert(nlp->paramval->varno == OUTER);
 				Assert(nlp->paramval->varattno > 0);
 				prm->value = slot_getattr(outerTupleSlot,
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 8243802199d..7a81010e4cf 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -27,6 +27,7 @@
 #include "optimizer/clauses.h"
 #include "optimizer/cost.h"
 #include "optimizer/paths.h"
+#include "optimizer/placeholder.h"
 #include "optimizer/plancat.h"
 #include "optimizer/planmain.h"
 #include "optimizer/predtest.h"
@@ -1886,7 +1887,20 @@ create_nestloop_plan(PlannerInfo *root,
 		NestLoopParam *nlp = (NestLoopParam *) lfirst(cell);
 
 		next = lnext(cell);
-		if (bms_is_member(nlp->paramval->varno, outerrelids))
+		if (IsA(nlp->paramval, Var) &&
+			bms_is_member(nlp->paramval->varno, outerrelids))
+		{
+			root->curOuterParams = list_delete_cell(root->curOuterParams,
+													cell, prev);
+			nestParams = lappend(nestParams, nlp);
+		}
+		else if (IsA(nlp->paramval, PlaceHolderVar) &&
+				 bms_overlap(((PlaceHolderVar *) nlp->paramval)->phrels,
+							 outerrelids) &&
+				 bms_is_subset(find_placeholder_info(root,
+													 (PlaceHolderVar *) nlp->paramval,
+													 false)->ph_eval_at,
+							   outerrelids))
 		{
 			root->curOuterParams = list_delete_cell(root->curOuterParams,
 													cell, prev);
@@ -2314,11 +2328,12 @@ create_hashjoin_plan(PlannerInfo *root,
 
 /*
  * replace_nestloop_params
- *	  Replace outer-relation Vars in the given expression with nestloop Params
+ *	  Replace outer-relation Vars and PlaceHolderVars in the given expression
+ *	  with nestloop Params
  *
- * All Vars belonging to the relation(s) identified by root->curOuterRels
- * are replaced by Params, and entries are added to root->curOuterParams if
- * not already present.
+ * All Vars and PlaceHolderVars belonging to the relation(s) identified by
+ * root->curOuterRels are replaced by Params, and entries are added to
+ * root->curOuterParams if not already present.
  */
 static Node *
 replace_nestloop_params(PlannerInfo *root, Node *expr)
@@ -2345,7 +2360,7 @@ replace_nestloop_params_mutator(Node *node, PlannerInfo *root)
 		if (!bms_is_member(var->varno, root->curOuterRels))
 			return node;
 		/* Create a Param representing the Var */
-		param = assign_nestloop_param(root, var);
+		param = assign_nestloop_param_var(root, var);
 		/* Is this param already listed in root->curOuterParams? */
 		foreach(lc, root->curOuterParams)
 		{
@@ -2365,6 +2380,48 @@ replace_nestloop_params_mutator(Node *node, PlannerInfo *root)
 		/* And return the replacement Param */
 		return (Node *) param;
 	}
+	if (IsA(node, PlaceHolderVar))
+	{
+		PlaceHolderVar *phv = (PlaceHolderVar *) node;
+		Param	   *param;
+		NestLoopParam *nlp;
+		ListCell   *lc;
+
+		/* Upper-level PlaceHolderVars should be long gone at this point */
+		Assert(phv->phlevelsup == 0);
+
+		/*
+		 * If not to be replaced, just return the PlaceHolderVar unmodified.
+		 * We use bms_overlap as a cheap/quick test to see if the PHV might
+		 * be evaluated in the outer rels, and then grab its PlaceHolderInfo
+		 * to tell for sure.
+		 */
+		if (!bms_overlap(phv->phrels, root->curOuterRels))
+			return node;
+		if (!bms_is_subset(find_placeholder_info(root, phv, false)->ph_eval_at,
+						   root->curOuterRels))
+			return node;
+		/* Create a Param representing the PlaceHolderVar */
+		param = assign_nestloop_param_placeholdervar(root, phv);
+		/* Is this param already listed in root->curOuterParams? */
+		foreach(lc, root->curOuterParams)
+		{
+			nlp = (NestLoopParam *) lfirst(lc);
+			if (nlp->paramno == param->paramid)
+			{
+				Assert(equal(phv, nlp->paramval));
+				/* Present, so we can just return the Param */
+				return (Node *) param;
+			}
+		}
+		/* No, so add it */
+		nlp = makeNode(NestLoopParam);
+		nlp->paramno = param->paramid;
+		nlp->paramval = (Var *) phv;
+		root->curOuterParams = lappend(root->curOuterParams, nlp);
+		/* And return the replacement Param */
+		return (Node *) param;
+	}
 	return expression_tree_mutator(node,
 								   replace_nestloop_params_mutator,
 								   (void *) root);
@@ -2377,7 +2434,7 @@ replace_nestloop_params_mutator(Node *node, PlannerInfo *root)
  *
  * We have four tasks here:
  *	* Remove RestrictInfo nodes from the input clauses.
- *	* Replace any outer-relation Var nodes with nestloop Params.
+ *	* Replace any outer-relation Var or PHV nodes with nestloop Params.
  *	  (XXX eventually, that responsibility should go elsewhere?)
  *	* Index keys must be represented by Var nodes with varattno set to the
  *	  index's attribute number, not the attribute number in the original rel.
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 60a1484c992..01d2cec562f 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -1019,6 +1019,10 @@ set_join_references(PlannerGlobal *glob, Join *join, int rtoffset)
 												   (Node *) nlp->paramval,
 												   outer_itlist,
 												   rtoffset);
+			/* Check we replaced any PlaceHolderVar with simple Var */
+			if (!(IsA(nlp->paramval, Var) &&
+				  nlp->paramval->varno == OUTER))
+				elog(ERROR, "NestLoopParam was not reduced to a simple Var");
 		}
 	}
 	else if (IsA(join, MergeJoin))
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 71ffc17b599..570151e6065 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -172,7 +172,7 @@ replace_outer_var(PlannerInfo *root, Var *var)
  * the Var to be local to the current query level.
  */
 Param *
-assign_nestloop_param(PlannerInfo *root, Var *var)
+assign_nestloop_param_var(PlannerInfo *root, Var *var)
 {
 	Param	   *retval;
 	int			i;
@@ -193,6 +193,65 @@ assign_nestloop_param(PlannerInfo *root, Var *var)
 }
 
 /*
+ * Generate a Param node to replace the given PlaceHolderVar, which will be
+ * supplied from an upper NestLoop join node.
+ *
+ * This is just like assign_nestloop_param_var, except for PlaceHolderVars.
+ */
+Param *
+assign_nestloop_param_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
+{
+	Param	   *retval;
+	ListCell   *ppl;
+	PlannerParamItem *pitem;
+	Index		abslevel;
+	int			i;
+
+	Assert(phv->phlevelsup == 0);
+	abslevel = root->query_level;
+
+	/* If there's already a paramlist entry for this same PHV, just use it */
+	/* We assume comparing the PHIDs is sufficient */
+	i = 0;
+	foreach(ppl, root->glob->paramlist)
+	{
+		pitem = (PlannerParamItem *) lfirst(ppl);
+		if (pitem->abslevel == abslevel && IsA(pitem->item, PlaceHolderVar))
+		{
+			PlaceHolderVar *pphv = (PlaceHolderVar *) pitem->item;
+
+			if (pphv->phid == phv->phid)
+				break;
+		}
+		i++;
+	}
+
+	if (ppl == NULL)
+	{
+		/* Nope, so make a new one */
+		phv = (PlaceHolderVar *) copyObject(phv);
+
+		pitem = makeNode(PlannerParamItem);
+		pitem->item = (Node *) phv;
+		pitem->abslevel = abslevel;
+
+		root->glob->paramlist = lappend(root->glob->paramlist, pitem);
+
+		/* i is already the correct list index for the new item */
+	}
+
+	retval = makeNode(Param);
+	retval->paramkind = PARAM_EXEC;
+	retval->paramid = i;
+	retval->paramtype = exprType((Node *) phv->phexpr);
+	retval->paramtypmod = exprTypmod((Node *) phv->phexpr);
+	retval->paramcollid = exprCollation((Node *) phv->phexpr);
+	retval->location = -1;
+
+	return retval;
+}
+
+/*
  * Generate a Param node to replace the given Aggref
  * which is expected to have agglevelsup > 0 (ie, it is not local).
  */