diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 860e9a2a06..828b33285d 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -802,10 +802,10 @@ exprCollation(const Node *expr)
 			coll = ((const NullIfExpr *) expr)->opcollid;
 			break;
 		case T_ScalarArrayOpExpr:
-			coll = InvalidOid;	/* result is always boolean */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_BoolExpr:
-			coll = InvalidOid;	/* result is always boolean */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_SubLink:
 			{
@@ -827,7 +827,7 @@ exprCollation(const Node *expr)
 				}
 				else
 				{
-					/* otherwise, result is RECORD or BOOLEAN */
+					/* otherwise, result is InvalidOid */
 					coll = InvalidOid;
 				}
 			}
@@ -845,7 +845,7 @@ exprCollation(const Node *expr)
 				}
 				else
 				{
-					/* otherwise, result is RECORD or BOOLEAN */
+					/* otherwise, result is InvalidOid */
 					coll = InvalidOid;
 				}
 			}
@@ -862,7 +862,7 @@ exprCollation(const Node *expr)
 			coll = ((const FieldSelect *) expr)->resultcollid;
 			break;
 		case T_FieldStore:
-			coll = InvalidOid;	/* result is always composite */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_RelabelType:
 			coll = ((const RelabelType *) expr)->resultcollid;
@@ -874,7 +874,7 @@ exprCollation(const Node *expr)
 			coll = ((const ArrayCoerceExpr *) expr)->resultcollid;
 			break;
 		case T_ConvertRowtypeExpr:
-			coll = InvalidOid;	/* result is always composite */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_CollateExpr:
 			coll = ((const CollateExpr *) expr)->collOid;
@@ -889,10 +889,10 @@ exprCollation(const Node *expr)
 			coll = ((const ArrayExpr *) expr)->array_collid;
 			break;
 		case T_RowExpr:
-			coll = InvalidOid;	/* result is always composite */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_RowCompareExpr:
-			coll = InvalidOid;	/* result is always boolean */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_CoalesceExpr:
 			coll = ((const CoalesceExpr *) expr)->coalescecollid;
@@ -920,10 +920,10 @@ exprCollation(const Node *expr)
 				coll = InvalidOid;
 			break;
 		case T_NullTest:
-			coll = InvalidOid;	/* result is always boolean */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_BooleanTest:
-			coll = InvalidOid;	/* result is always boolean */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_CoerceToDomain:
 			coll = ((const CoerceToDomain *) expr)->resultcollid;
@@ -935,10 +935,10 @@ exprCollation(const Node *expr)
 			coll = ((const SetToDefault *) expr)->collation;
 			break;
 		case T_CurrentOfExpr:
-			coll = InvalidOid;	/* result is always boolean */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_NextValueExpr:
-			coll = InvalidOid;	/* result is always an integer type */
+			coll = InvalidOid;	/* result is always InvalidOid */
 			break;
 		case T_InferenceElem:
 			coll = exprCollation((Node *) ((const InferenceElem *) expr)->expr);
@@ -1050,10 +1050,10 @@ exprSetCollation(Node *expr, Oid collation)
 			((NullIfExpr *) expr)->opcollid = collation;
 			break;
 		case T_ScalarArrayOpExpr:
-			Assert(!OidIsValid(collation)); /* result is always boolean */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_BoolExpr:
-			Assert(!OidIsValid(collation)); /* result is always boolean */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_SubLink:
 #ifdef USE_ASSERT_CHECKING
@@ -1085,7 +1085,7 @@ exprSetCollation(Node *expr, Oid collation)
 			((FieldSelect *) expr)->resultcollid = collation;
 			break;
 		case T_FieldStore:
-			Assert(!OidIsValid(collation)); /* result is always composite */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_RelabelType:
 			((RelabelType *) expr)->resultcollid = collation;
@@ -1097,7 +1097,7 @@ exprSetCollation(Node *expr, Oid collation)
 			((ArrayCoerceExpr *) expr)->resultcollid = collation;
 			break;
 		case T_ConvertRowtypeExpr:
-			Assert(!OidIsValid(collation)); /* result is always composite */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_CaseExpr:
 			((CaseExpr *) expr)->casecollid = collation;
@@ -1106,10 +1106,10 @@ exprSetCollation(Node *expr, Oid collation)
 			((ArrayExpr *) expr)->array_collid = collation;
 			break;
 		case T_RowExpr:
-			Assert(!OidIsValid(collation)); /* result is always composite */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_RowCompareExpr:
-			Assert(!OidIsValid(collation)); /* result is always boolean */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_CoalesceExpr:
 			((CoalesceExpr *) expr)->coalescecollid = collation;
@@ -1128,10 +1128,10 @@ exprSetCollation(Node *expr, Oid collation)
 				   (collation == InvalidOid));
 			break;
 		case T_NullTest:
-			Assert(!OidIsValid(collation)); /* result is always boolean */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_BooleanTest:
-			Assert(!OidIsValid(collation)); /* result is always boolean */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_CoerceToDomain:
 			((CoerceToDomain *) expr)->resultcollid = collation;
@@ -1143,11 +1143,10 @@ exprSetCollation(Node *expr, Oid collation)
 			((SetToDefault *) expr)->collation = collation;
 			break;
 		case T_CurrentOfExpr:
-			Assert(!OidIsValid(collation)); /* result is always boolean */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		case T_NextValueExpr:
-			Assert(!OidIsValid(collation)); /* result is always an integer
-											 * type */
+			Assert(!OidIsValid(collation)); /* must never be a valid Oid */
 			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));