Align vector ordering tests with ScalarValue NULL partial_cmp semantics

Author: Brijesh-Thakkar

datafusion/common/src/scalar/mod.rs

@@ -727,8 +727,10 @@ impl PartialOrd for ScalarValue {
                 if k1 == k2 { v1.partial_cmp(v2) } else { None }
             }
             (Dictionary(_, _), _) => None,
-            // Null is handled by the early return above, but we need this for exhaustiveness
-            (Null, _) => None,
+            // Nulls are handled by the early return above
+            (Null, _) | (_, Null) => unreachable!(
+                "Nulls are already handled before entering ScalarValue::partial_cmp match"
+            ),
         }
     }
 }

datafusion/common/src/utils/mod.rs

@@ -1021,29 +1021,33 @@ mod tests {
     fn vector_ord() {
         assert!(vec![1, 0, 0, 0, 0, 0, 0, 1] < vec![1, 0, 0, 0, 0, 0, 0, 2]);
         assert!(vec![1, 0, 0, 0, 0, 0, 1, 1] > vec![1, 0, 0, 0, 0, 0, 0, 2]);
-        assert!(
+        // Vectors containing Null values cannot be compared because
+        // ScalarValue::partial_cmp returns None for null comparisons
+        assert_eq!(
             vec![
                 ScalarValue::Int32(Some(2)),
                 Null,
                 ScalarValue::Int32(Some(0)),
             ]
-            < vec![
+            .partial_cmp(&vec![
                 ScalarValue::Int32(Some(2)),
                 Null,
                 ScalarValue::Int32(Some(1)),
-            ]
+            ]),
+            None
         );
-        assert!(
+        assert_eq!(
             vec![
                 ScalarValue::Int32(Some(2)),
                 ScalarValue::Int32(None),
                 ScalarValue::Int32(Some(0)),
             ]
-            < vec![
+            .partial_cmp(&vec![
                 ScalarValue::Int32(Some(2)),
                 ScalarValue::Int32(None),
                 ScalarValue::Int32(Some(1)),
-            ]
+            ]),
+            None
         );
     }