Make SubPlan nodes carry the result's typmod as well as datatype OID. This is

for consistency with the (relatively) recent addition of typmod to SubLink.
An example of why it's a good idea is to be seen in the recent "failed to
locate grouping columns" bug, which wouldn't have happened if a SubPlan
exposed the same typmod info as the SubLink it was derived from.

This could be back-patched, since it doesn't affect any on-disk data format,
but for the moment it doesn't seem necessary to do so.

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.425 2009/02/25 03:30:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.426 2009/03/10 22:09:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1113,6 +1113,7 @@ _copySubPlan(SubPlan *from)
 	COPY_NODE_FIELD(paramIds);
 	COPY_SCALAR_FIELD(plan_id);
 	COPY_SCALAR_FIELD(firstColType);
+	COPY_SCALAR_FIELD(firstColTypmod);
 	COPY_SCALAR_FIELD(useHashTable);
 	COPY_SCALAR_FIELD(unknownEqFalse);
 	COPY_NODE_FIELD(setParam);

src/backend/nodes/equalfuncs.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.349 2009/02/25 03:30:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.350 2009/03/10 22:09:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -342,6 +342,7 @@ _equalSubPlan(SubPlan *a, SubPlan *b)
 	COMPARE_NODE_FIELD(paramIds);
 	COMPARE_SCALAR_FIELD(plan_id);
 	COMPARE_SCALAR_FIELD(firstColType);
+	COMPARE_SCALAR_FIELD(firstColTypmod);
 	COMPARE_SCALAR_FIELD(useHashTable);
 	COMPARE_SCALAR_FIELD(unknownEqFalse);
 	COMPARE_NODE_FIELD(setParam);

src/backend/nodes/nodeFuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/nodeFuncs.c,v 1.38 2009/02/25 03:30:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/nodeFuncs.c,v 1.39 2009/03/10 22:09:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -28,7 +28,7 @@ static int	leftmostLoc(int loc1, int loc2);
 
 /*
  *	exprType -
- *	  returns the Oid of the type of the expression. (Used for typechecking.)
+ *	  returns the Oid of the type of the expression's result.
  */
 Oid
 exprType(Node *expr)
@@ -117,11 +117,6 @@ exprType(Node *expr)
 			break;
 		case T_SubPlan:
 			{
-				/*
-				 * Although the parser does not ever deal with already-planned
-				 * expression trees, we support SubPlan nodes in this routine
-				 * for the convenience of ruleutils.c.
-				 */
 				SubPlan    *subplan = (SubPlan *) expr;
 
 				if (subplan->subLinkType == EXPR_SUBLINK ||
@@ -148,7 +143,6 @@ exprType(Node *expr)
 			break;
 		case T_AlternativeSubPlan:
 			{
-				/* As above, supported for the convenience of ruleutils.c */
 				AlternativeSubPlan *asplan = (AlternativeSubPlan *) expr;
 
 				/* subplans should all return the same thing */
@@ -236,8 +230,8 @@ exprType(Node *expr)
 
 /*
  *	exprTypmod -
- *	  returns the type-specific attrmod of the expression, if it can be
+ *	  returns the type-specific modifier of the expression's result type,
- *	  determined.  In most cases, it can't and we return -1.
+ *	  if it can be determined.  In many cases, it can't and we return -1.
  */
 int32
 exprTypmod(Node *expr)
@@ -286,6 +280,32 @@ exprTypmod(Node *expr)
 				}
 			}
 			break;
+		case T_SubPlan:
+			{
+				SubPlan    *subplan = (SubPlan *) expr;
+
+				if (subplan->subLinkType == EXPR_SUBLINK ||
+					subplan->subLinkType == ARRAY_SUBLINK)
+				{
+					/* get the typmod of the subselect's first target column */
+					/* note we don't need to care if it's an array */
+					return subplan->firstColTypmod;
+				}
+				else
+				{
+					/* for all other subplan types, result is boolean */
+					return -1;
+				}
+			}
+			break;
+		case T_AlternativeSubPlan:
+			{
+				AlternativeSubPlan *asplan = (AlternativeSubPlan *) expr;
+
+				/* subplans should all return the same thing */
+				return exprTypmod((Node *) linitial(asplan->subplans));
+			}
+			break;
 		case T_FieldSelect:
 			return ((FieldSelect *) expr)->resulttypmod;
 		case T_RelabelType:

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.353 2009/02/25 03:30:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.354 2009/03/10 22:09:25 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -957,6 +957,7 @@ _outSubPlan(StringInfo str, SubPlan *node)
 	WRITE_NODE_FIELD(paramIds);
 	WRITE_INT_FIELD(plan_id);
 	WRITE_OID_FIELD(firstColType);
+	WRITE_INT_FIELD(firstColTypmod);
 	WRITE_BOOL_FIELD(useHashTable);
 	WRITE_BOOL_FIELD(unknownEqFalse);
 	WRITE_NODE_FIELD(setParam);

src/backend/optimizer/plan/subselect.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.146 2009/02/25 03:30:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.147 2009/03/10 22:09:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -229,13 +229,13 @@ SS_assign_worktable_param(PlannerInfo *root)
 /*
  * Get the datatype of the first column of the plan's output.
  *
- * This is stored for ARRAY_SUBLINK and for exprType(), which doesn't have any
+ * This is stored for ARRAY_SUBLINK execution and for exprType()/exprTypmod(),
- * way to get at the plan associated with a SubPlan node.  We really only need
+ * which have no way to get at the plan associated with a SubPlan node.
- * the value for EXPR_SUBLINK and ARRAY_SUBLINK subplans, but for consistency
+ * We really only need the info for EXPR_SUBLINK and ARRAY_SUBLINK subplans,
- * we set it always.
+ * but for consistency we save it always.
  */
-static Oid
+static void
-get_first_col_type(Plan *plan)
+get_first_col_type(Plan *plan, Oid *coltype, int32 *coltypmod)
 {
 	/* In cases such as EXISTS, tlist might be empty; arbitrarily use VOID */
 	if (plan->targetlist)
@@ -244,9 +244,14 @@ get_first_col_type(Plan *plan)
 
 		Assert(IsA(tent, TargetEntry));
 		if (!tent->resjunk)
-			return exprType((Node *) tent->expr);
+		{
+			*coltype = exprType((Node *) tent->expr);
+			*coltypmod = exprTypmod((Node *) tent->expr);
+			return;
+		}
 	}
-	return VOIDOID;
+	*coltype = VOIDOID;
+	*coltypmod = -1;
 }
 
 /*
@@ -414,7 +419,7 @@ build_subplan(PlannerInfo *root, Plan *plan, List *rtable,
 	splan->subLinkType = subLinkType;
 	splan->testexpr = NULL;
 	splan->paramIds = NIL;
-	splan->firstColType = get_first_col_type(plan);
+	get_first_col_type(plan, &splan->firstColType, &splan->firstColTypmod);
 	splan->useHashTable = false;
 	splan->unknownEqFalse = unknownEqFalse;
 	splan->setParam = NIL;
@@ -876,7 +881,7 @@ SS_process_ctes(PlannerInfo *root)
 		splan->subLinkType = CTE_SUBLINK;
 		splan->testexpr = NULL;
 		splan->paramIds = NIL;
-		splan->firstColType = get_first_col_type(plan);
+		get_first_col_type(plan, &splan->firstColType, &splan->firstColTypmod);
 		splan->useHashTable = false;
 		splan->unknownEqFalse = false;
 		splan->setParam = NIL;
@@ -2111,7 +2116,7 @@ SS_make_initplan_from_plan(PlannerInfo *root, Plan *plan,
 	 */
 	node = makeNode(SubPlan);
 	node->subLinkType = EXPR_SUBLINK;
-	node->firstColType = get_first_col_type(plan);
+	get_first_col_type(plan, &node->firstColType, &node->firstColTypmod);
 	node->plan_id = list_length(root->glob->subplans);
 
 	root->init_plans = lappend(root->init_plans, node);

src/include/nodes/primnodes.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.146 2009/02/25 03:30:37 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.147 2009/03/10 22:09:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -504,6 +504,7 @@ typedef struct SubPlan
 	int			plan_id;		/* Index (from 1) in PlannedStmt.subplans */
 	/* Extra data useful for determining subplan's output type: */
 	Oid			firstColType;	/* Type of first column of subplan result */
+	int32		firstColTypmod;	/* Typmod of first column of subplan result */
 	/* Information about execution strategy: */
 	bool		useHashTable;	/* TRUE to store subselect output in a hash
 								 * table (implies we are doing "IN") */