3 files changed, 23 insertions, 11 deletions

diff --git a/src/backend/optimizer/util/appendinfo.c b/src/backend/optimizer/util/appendinfo.c
index 2f06fa743c2..9d4bb470270 100644
--- a/src/backend/optimizer/util/appendinfo.c
+++ b/src/backend/optimizer/util/appendinfo.c
@@ -774,8 +774,8 @@ add_row_identity_var(PlannerInfo *root, Var *orig_var,
 	Assert(orig_var->varlevelsup == 0);
 
 	/*
-	 * If we're doing non-inherited UPDATE/DELETE, there's little need for
-	 * ROWID_VAR shenanigans.  Just shove the presented Var into the
+	 * If we're doing non-inherited UPDATE/DELETE/MERGE, there's little need
+	 * for ROWID_VAR shenanigans.  Just shove the presented Var into the
 	 * processed_tlist, and we're done.
 	 */
 	if (rtindex == root->parse->resultRelation)
@@ -862,14 +862,16 @@ add_row_identity_columns(PlannerInfo *root, Index rtindex,
 	char		relkind = target_relation->rd_rel->relkind;
 	Var		   *var;
 
-	Assert(commandType == CMD_UPDATE || commandType == CMD_DELETE);
+	Assert(commandType == CMD_UPDATE || commandType == CMD_DELETE || commandType == CMD_MERGE);
 
-	if (relkind == RELKIND_RELATION ||
+	if (commandType == CMD_MERGE ||
+		relkind == RELKIND_RELATION ||
 		relkind == RELKIND_MATVIEW ||
 		relkind == RELKIND_PARTITIONED_TABLE)
 	{
 		/*
-		 * Emit CTID so that executor can find the row to update or delete.
+		 * Emit CTID so that executor can find the row to merge, update or
+		 * delete.
 		 */
 		var = makeVar(rtindex,
 					  SelfItemPointerAttributeNumber,
@@ -942,8 +944,11 @@ distribute_row_identity_vars(PlannerInfo *root)
 	RelOptInfo *target_rel;
 	ListCell   *lc;
 
-	/* There's nothing to do if this isn't an inherited UPDATE/DELETE. */
-	if (parse->commandType != CMD_UPDATE && parse->commandType != CMD_DELETE)
+	/*
+	 * There's nothing to do if this isn't an inherited UPDATE/DELETE/MERGE.
+	 */
+	if (parse->commandType != CMD_UPDATE && parse->commandType != CMD_DELETE &&
+		parse->commandType != CMD_MERGE)
 	{
 		Assert(root->row_identity_vars == NIL);
 		return;
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 5c32c96b71c..99df76b6b71 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -3620,6 +3620,7 @@ create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
  * 'rowMarks' is a list of PlanRowMarks (non-locking only)
  * 'onconflict' is the ON CONFLICT clause, or NULL
  * 'epqParam' is the ID of Param for EvalPlanQual re-eval
+ * 'mergeActionLists' is a list of lists of MERGE actions (one per rel)
  */
 ModifyTablePath *
 create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
@@ -3631,13 +3632,14 @@ create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 						List *updateColnosLists,
 						List *withCheckOptionLists, List *returningLists,
 						List *rowMarks, OnConflictExpr *onconflict,
-						int epqParam)
+						List *mergeActionLists, int epqParam)
 {
 	ModifyTablePath *pathnode = makeNode(ModifyTablePath);
 
-	Assert(operation == CMD_UPDATE ?
-		   list_length(resultRelations) == list_length(updateColnosLists) :
-		   updateColnosLists == NIL);
+	Assert(operation == CMD_MERGE ||
+		   (operation == CMD_UPDATE ?
+			list_length(resultRelations) == list_length(updateColnosLists) :
+			updateColnosLists == NIL));
 	Assert(withCheckOptionLists == NIL ||
 		   list_length(resultRelations) == list_length(withCheckOptionLists));
 	Assert(returningLists == NIL ||
@@ -3697,6 +3699,7 @@ create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 	pathnode->rowMarks = rowMarks;
 	pathnode->onconflict = onconflict;
 	pathnode->epqParam = epqParam;
+	pathnode->mergeActionLists = mergeActionLists;
 
 	return pathnode;
 }
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index a5002ad8955..df97b799174 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -2167,6 +2167,10 @@ has_row_triggers(PlannerInfo *root, Index rti, CmdType event)
 				 trigDesc->trig_delete_before_row))
 				result = true;
 			break;
+			/* There is no separate event for MERGE, only INSERT/UPDATE/DELETE */
+		case CMD_MERGE:
+			result = false;
+			break;
 		default:
 			elog(ERROR, "unrecognized CmdType: %d", (int) event);
 			break;