fix: correct stale unix_timestamp NTZ and date_format codegen-default doc text (#4502)

native/spark-expr/src/datetime_funcs/date_diff.rs

@@ -100,9 +100,12 @@ impl ScalarUDFImpl for SparkDateDiff {
                 )
             })?;
 
-        // Date32 stores days since epoch, so difference is just subtraction
-        let result: Int32Array =
-            binary(end_date_array, start_date_array, |end, start| end - start)?;
+        // Date32 stores days since epoch, so difference is just subtraction. Use wrapping_sub
+        // to match Spark, whose JVM int subtraction wraps on overflow; a plain `i32 -` would
+        // panic in debug builds on extreme inputs.
+        let result: Int32Array = binary(end_date_array, start_date_array, |end, start| {
+            end.wrapping_sub(start)
+        })?;
 
         Ok(ColumnarValue::Array(Arc::new(result)))
     }
@@ -111,3 +114,53 @@ impl ScalarUDFImpl for SparkDateDiff {
         &self.aliases
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use arrow::datatypes::Field;
+    use datafusion::config::ConfigOptions;
+
+    fn date_diff(end: i32, start: i32) -> i32 {
+        let udf = SparkDateDiff::new();
+        let return_field = Arc::new(Field::new("date_diff", DataType::Int32, true));
+        let args = ScalarFunctionArgs {
+            args: vec![
+                ColumnarValue::Array(Arc::new(Date32Array::from(vec![Some(end)]))),
+                ColumnarValue::Array(Arc::new(Date32Array::from(vec![Some(start)]))),
+            ],
+            number_rows: 1,
+            return_field,
+            config_options: Arc::new(ConfigOptions::default()),
+            arg_fields: vec![],
+        };
+        match udf.invoke_with_args(args).unwrap() {
+            ColumnarValue::Array(array) => array
+                .as_any()
+                .downcast_ref::<Int32Array>()
+                .unwrap()
+                .value(0),
+            _ => panic!("expected array result"),
+        }
+    }
+
+    #[test]
+    fn test_date_diff_basic() {
+        // 2020-01-02 (18263) minus 2020-01-01 (18262) = 1 day
+        assert_eq!(date_diff(18263, 18262), 1);
+        assert_eq!(date_diff(18262, 18263), -1);
+    }
+
+    #[test]
+    fn test_date_diff_wraps_on_overflow() {
+        // Extreme inputs overflow i32; Spark's JVM int subtraction wraps rather than panicking.
+        assert_eq!(
+            date_diff(i32::MAX, i32::MIN),
+            i32::MAX.wrapping_sub(i32::MIN)
+        );
+        assert_eq!(
+            date_diff(i32::MIN, i32::MAX),
+            i32::MIN.wrapping_sub(i32::MAX)
+        );
+    }
+}

spark/src/main/scala/org/apache/comet/serde/datetime.scala

@@ -292,9 +292,7 @@ object CometSecond extends CometExpressionSerde[Second] with CodegenDispatchFall
 object CometUnixTimestamp extends CometExpressionSerde[UnixTimestamp] {
 
   override def getUnsupportedReasons(): Seq[String] = Seq(
-    "Only `TimestampType` and `DateType` inputs are supported." +
-      " `TimestampNTZType` is not supported because Comet incorrectly applies timezone" +
-      " conversion to TimestampNTZ values.")
+    "Only `DateType`, `TimestampType`, and `TimestampNTZType` inputs are supported.")
 
   private def isSupportedInputType(expr: UnixTimestamp): Boolean = {
     expr.children.head.dataType match {
@@ -695,9 +693,8 @@ object CometDateFormat extends CometExpressionSerde[DateFormatClass] {
     "Format strings in a curated allow-list run natively via DataFusion's `to_char` for UTC " +
       "sessions. Other format strings (including non-literal formats), as well as non-UTC " +
       "sessions, route through Spark's own `DateFormatClass.doGenCode` via the Arrow-direct " +
-      "codegen dispatcher when `spark.comet.exec.scalaUDF.codegen.enabled=true`. When the " +
-      "codegen dispatcher is disabled (default) the operator falls back to Spark in those " +
-      "cases.")
+      "codegen dispatcher when `spark.comet.exec.scalaUDF.codegen.enabled=true` (the default). " +
+      "When the codegen dispatcher is disabled the operator falls back to Spark in those cases.")
 
   override def convert(
       expr: DateFormatClass,