1 files changed, 28 insertions, 35 deletions

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index d5c66780ac8..1c47a2fb49c 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -3540,6 +3540,7 @@ create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
  *	  Creates a pathnode that represents performing INSERT/UPDATE/DELETE mods
  *
  * 'rel' is the parent relation associated with the result
+ * 'subpath' is a Path producing source data
  * 'operation' is the operation type
  * 'canSetTag' is true if we set the command tag/es_processed
  * 'nominalRelation' is the parent RT index for use of EXPLAIN
@@ -3547,8 +3548,8 @@ create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
  * 'partColsUpdated' is true if any partitioning columns are being updated,
  *		either from the target relation or a descendent partitioned table.
  * 'resultRelations' is an integer list of actual RT indexes of target rel(s)
- * 'subpaths' is a list of Path(s) producing source data (one per rel)
- * 'subroots' is a list of PlannerInfo structs (one per rel)
+ * 'updateColnosLists' is a list of UPDATE target column number lists
+ *		(one sublist per rel); or NIL if not an UPDATE
  * 'withCheckOptionLists' is a list of WCO lists (one per rel)
  * 'returningLists' is a list of RETURNING tlists (one per rel)
  * 'rowMarks' is a list of PlanRowMarks (non-locking only)
@@ -3557,21 +3558,21 @@ create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
  */
 ModifyTablePath *
 create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
+						Path *subpath,
 						CmdType operation, bool canSetTag,
 						Index nominalRelation, Index rootRelation,
 						bool partColsUpdated,
-						List *resultRelations, List *subpaths,
-						List *subroots,
+						List *resultRelations,
+						List *updateColnosLists,
 						List *withCheckOptionLists, List *returningLists,
 						List *rowMarks, OnConflictExpr *onconflict,
 						int epqParam)
 {
 	ModifyTablePath *pathnode = makeNode(ModifyTablePath);
-	double		total_size;
-	ListCell   *lc;
 
-	Assert(list_length(resultRelations) == list_length(subpaths));
-	Assert(list_length(resultRelations) == list_length(subroots));
+	Assert(operation == CMD_UPDATE ?
+		   list_length(resultRelations) == list_length(updateColnosLists) :
+		   updateColnosLists == NIL);
 	Assert(withCheckOptionLists == NIL ||
 		   list_length(resultRelations) == list_length(withCheckOptionLists));
 	Assert(returningLists == NIL ||
@@ -3589,7 +3590,7 @@ create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 	pathnode->path.pathkeys = NIL;
 
 	/*
-	 * Compute cost & rowcount as sum of subpath costs & rowcounts.
+	 * Compute cost & rowcount as subpath cost & rowcount (if RETURNING)
 	 *
 	 * Currently, we don't charge anything extra for the actual table
 	 * modification work, nor for the WITH CHECK OPTIONS or RETURNING
@@ -3598,42 +3599,34 @@ create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 	 * costs to change any higher-level planning choices.  But we might want
 	 * to make it look better sometime.
 	 */
-	pathnode->path.startup_cost = 0;
-	pathnode->path.total_cost = 0;
-	pathnode->path.rows = 0;
-	total_size = 0;
-	foreach(lc, subpaths)
+	pathnode->path.startup_cost = subpath->startup_cost;
+	pathnode->path.total_cost = subpath->total_cost;
+	if (returningLists != NIL)
 	{
-		Path	   *subpath = (Path *) lfirst(lc);
+		pathnode->path.rows = subpath->rows;
 
-		if (lc == list_head(subpaths))	/* first node? */
-			pathnode->path.startup_cost = subpath->startup_cost;
-		pathnode->path.total_cost += subpath->total_cost;
-		if (returningLists != NIL)
-		{
-			pathnode->path.rows += subpath->rows;
-			total_size += subpath->pathtarget->width * subpath->rows;
-		}
+		/*
+		 * Set width to match the subpath output.  XXX this is totally wrong:
+		 * we should return an average of the RETURNING tlist widths.  But
+		 * it's what happened historically, and improving it is a task for
+		 * another day.  (Again, it's mostly window dressing.)
+		 */
+		pathnode->path.pathtarget->width = subpath->pathtarget->width;
+	}
+	else
+	{
+		pathnode->path.rows = 0;
+		pathnode->path.pathtarget->width = 0;
 	}
 
-	/*
-	 * Set width to the average width of the subpath outputs.  XXX this is
-	 * totally wrong: we should return an average of the RETURNING tlist
-	 * widths.  But it's what happened historically, and improving it is a task
-	 * for another day.
-	 */
-	if (pathnode->path.rows > 0)
-		total_size /= pathnode->path.rows;
-	pathnode->path.pathtarget->width = rint(total_size);
-
+	pathnode->subpath = subpath;
 	pathnode->operation = operation;
 	pathnode->canSetTag = canSetTag;
 	pathnode->nominalRelation = nominalRelation;
 	pathnode->rootRelation = rootRelation;
 	pathnode->partColsUpdated = partColsUpdated;
 	pathnode->resultRelations = resultRelations;
-	pathnode->subpaths = subpaths;
-	pathnode->subroots = subroots;
+	pathnode->updateColnosLists = updateColnosLists;
 	pathnode->withCheckOptionLists = withCheckOptionLists;
 	pathnode->returningLists = returningLists;
 	pathnode->rowMarks = rowMarks;