diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 62355aa..4b4ddec 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -112,6 +112,7 @@ CopyPlanFields(const Plan *from, Plan *newnode)
 	COPY_SCALAR_FIELD(total_cost);
 	COPY_SCALAR_FIELD(plan_rows);
 	COPY_SCALAR_FIELD(plan_width);
+	COPY_SCALAR_FIELD(plan_node_id);
 	COPY_NODE_FIELD(targetlist);
 	COPY_NODE_FIELD(qual);
 	COPY_NODE_FIELD(lefttree);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index e1b49d5..d7d00c0 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -269,6 +269,7 @@ _outPlanInfo(StringInfo str, const Plan *node)
 	WRITE_FLOAT_FIELD(total_cost, "%.2f");
 	WRITE_FLOAT_FIELD(plan_rows, "%.0f");
 	WRITE_INT_FIELD(plan_width);
+	WRITE_INT_FIELD(plan_node_id);
 	WRITE_NODE_FIELD(targetlist);
 	WRITE_NODE_FIELD(qual);
 	WRITE_NODE_FIELD(lefttree);
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 06be922..e1ee67c 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -196,6 +196,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 	glob->nParamExec = 0;
 	glob->lastPHId = 0;
 	glob->lastRowMarkId = 0;
+	glob->lastPlanNodeId = 0;
 	glob->transientPlan = false;
 	glob->hasRowSecurity = false;
 
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index daeb584..e3e1a1d 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -174,6 +174,8 @@ static bool extract_query_dependencies_walker(Node *node,
  * Currently, relations and user-defined functions are the only types of
  * objects that are explicitly tracked this way.
  *
+ * 7. We assign every plan node in the tree a unique ID.
+ *
  * We also perform one final optimization step, which is to delete
  * SubqueryScan plan nodes that aren't doing anything useful (ie, have
  * no qual and a no-op targetlist).  The reason for doing this last is that
@@ -437,6 +439,12 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 		return NULL;
 
 	/*
+	 * Assign this node a unique ID.  We want to do this before traversing
+	 * subplans so that every Plan has an ID greater than that of its parent.
+	 */
+	plan->plan_node_id = root->glob->lastPlanNodeId++;
+
+	/*
 	 * Plan-type-specific fixes
 	 */
 	switch (nodeTag(plan))
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index cc259f1..1e2d2bb 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -111,6 +111,7 @@ typedef struct Plan
 	/*
 	 * Common structural data for all Plan types.
 	 */
+	int			plan_node_id;	/* unique across entire final plan tree */
 	List	   *targetlist;		/* target list to be computed at this node */
 	List	   *qual;			/* implicitly-ANDed qual conditions */
 	struct Plan *lefttree;		/* input plan tree(s) */
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 79bed33..961b5d1 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -99,6 +99,8 @@ typedef struct PlannerGlobal
 
 	Index		lastRowMarkId;	/* highest PlanRowMark ID assigned */
 
+	int			lastPlanNodeId;	/* highest plan node ID assigned */
+
 	bool		transientPlan;	/* redo plan when TransactionXmin changes? */
 
 	bool		hasRowSecurity; /* row security applied? */