1 files changed, 22 insertions, 0 deletions
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index c5fe6b6a3fd..a8549e0c2a7 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -2278,3 +2278,25 @@ transformFrameOffset(ParseState *pstate, int frameOptions, Node *clause)
 
 	return node;
 }
+
+/*
+ * relabel_to_typmod
+ *		Add a RelabelType node that changes just the typmod, and remove all
+ *		now-superfluous RelabelType nodes beneath it.
+ */
+Node *
+relabel_to_typmod(Node *expr, int32 typmod)
+{
+	Oid			type = exprType(expr);
+	Oid			coll = exprCollation(expr);
+
+	/*
+	 * Strip any existing RelabelType, then add one. This is to preserve the
+	 * invariant of no redundant RelabelTypes.
+	 */
+	while (IsA(expr, RelabelType))
+		expr = (Node *) ((RelabelType *) expr)->arg;
+
+	return (Node *) makeRelabelType((Expr *) expr, type, typmod, coll,
+									COERCE_DONTCARE);
+}