[GitHub] [arrow-rs] aprimadi commented on a diff in pull request #4201: Fix incorrect cast Timestamp with Timezone

[via GitHub]

aprimadi commented on code in PR #4201:
URL: https://github.com/apache/arrow-rs/pull/4201#discussion_r1192309724


##########
arrow-cast/src/cast.rs:
##########
@@ -5978,6 +6050,174 @@ mod tests {
         assert!(b.is_err());
     }
 
+    // Cast Timestamp(_, None) -> Timestamp(_, Some(timezone))
+    #[test]
+    fn test_cast_timestamp_with_timezone_1() {
+        let string_array: Arc<dyn Array> = Arc::new(StringArray::from(vec![
+            Some("2000-01-01T00:00:00.123456789"),
+            Some("2010-01-01T00:00:00.123456789"),
+            None,
+        ]));
+        let to_type = DataType::Timestamp(TimeUnit::Nanosecond, None);
+        let timestamp_array = cast(&string_array, &to_type).unwrap();
+
+        let to_type = DataType::Timestamp(TimeUnit::Microsecond, 
Some("+0700".into()));
+        let timestamp_array = cast(&timestamp_array, &to_type).unwrap();
+
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T00:00:00.123456+07:00", result.value(0));
+        assert_eq!("2010-01-01T00:00:00.123456+07:00", result.value(1));
+        assert!(result.is_null(2));
+    }
+
+    // Cast Timestamp(_, Some(timezone)) -> Timestamp(_, None)
+    #[test]
+    fn test_cast_timestamp_with_timezone_2() {
+        let string_array: Arc<dyn Array> = Arc::new(StringArray::from(vec![
+            Some("2000-01-01T07:00:00.123456789"),
+            Some("2010-01-01T07:00:00.123456789"),
+            None,
+        ]));
+        let to_type = DataType::Timestamp(TimeUnit::Millisecond, 
Some("+0700".into()));
+        let timestamp_array = cast(&string_array, &to_type).unwrap();
+
+        // Check intermediate representation is correct
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T07:00:00.123+07:00", result.value(0));
+        assert_eq!("2010-01-01T07:00:00.123+07:00", result.value(1));
+        assert!(result.is_null(2));
+
+        let to_type = DataType::Timestamp(TimeUnit::Nanosecond, None);
+        let timestamp_array = cast(&timestamp_array, &to_type).unwrap();
+
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T00:00:00.123", result.value(0));
+        assert_eq!("2010-01-01T00:00:00.123", result.value(1));
+        assert!(result.is_null(2));
+    }
+
+    // Cast Timestamp(_, Some(timezone)) -> Timestamp(_, Some(timezone))
+    #[test]
+    fn test_cast_timestamp_with_timezone_3() {
+        let string_array: Arc<dyn Array> = Arc::new(StringArray::from(vec![
+            Some("2000-01-01T07:00:00.123456789"),
+            Some("2010-01-01T07:00:00.123456789"),
+            None,
+        ]));
+        let to_type = DataType::Timestamp(TimeUnit::Microsecond, 
Some("+0700".into()));
+        let timestamp_array = cast(&string_array, &to_type).unwrap();
+
+        // Check intermediate representation is correct
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T07:00:00.123456+07:00", result.value(0));
+        assert_eq!("2010-01-01T07:00:00.123456+07:00", result.value(1));
+        assert!(result.is_null(2));
+
+        let to_type = DataType::Timestamp(TimeUnit::Second, 
Some("-08:00".into()));
+        let timestamp_array = cast(&timestamp_array, &to_type).unwrap();
+
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("1999-12-31T16:00:00-08:00", result.value(0));
+        assert_eq!("2009-12-31T16:00:00-08:00", result.value(1));
+        assert!(result.is_null(2));
+    }
+
+    // See: https://en.wikipedia.org/wiki/List_of_tz_database_time_zones for 
list of valid
+    // timezones
+
+    // Cast Timestamp(_, None) -> Timestamp(_, Some(timezone))
+    #[cfg(feature = "chrono-tz")]
+    #[test]
+    fn test_cast_timestamp_with_timezone_daylight_1() {
+        let string_array: Arc<dyn Array> = Arc::new(StringArray::from(vec![
+            // This is winter in New York so daylight saving is not in effect
+            // UTC offset is -05:00
+            Some("2000-01-01T00:00:00.123456789"),
+            // This is summer in New York so daylight saving is in effect
+            // UTC offset is -04:00
+            Some("2010-07-01T00:00:00.123456789"),
+            None,
+        ]));
+        let to_type = DataType::Timestamp(TimeUnit::Nanosecond, None);
+        let timestamp_array = cast(&string_array, &to_type).unwrap();
+
+        let to_type = DataType::Timestamp(TimeUnit::Microsecond, 
Some("America/New_York".into()));
+        let timestamp_array = cast(&timestamp_array, &to_type).unwrap();
+
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T00:00:00.123456-05:00", result.value(0));
+        assert_eq!("2010-07-01T00:00:00.123456-04:00", result.value(1));
+        assert!(result.is_null(2));
+    }
+
+    // Cast Timestamp(_, Some(timezone)) -> Timestamp(_, None)
+    #[cfg(feature = "chrono-tz")]
+    #[test]
+    fn test_cast_timestamp_with_timezone_daylight_2() {
+        let string_array: Arc<dyn Array> = Arc::new(StringArray::from(vec![
+            Some("2000-01-01T07:00:00.123456789"),
+            Some("2010-07-01T07:00:00.123456789"),
+            None,
+        ]));
+        let to_type = DataType::Timestamp(TimeUnit::Millisecond, 
Some("America/New_York".into()));
+        let timestamp_array = cast(&string_array, &to_type).unwrap();
+
+        // Check intermediate representation is correct
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T07:00:00.123-05:00", result.value(0));
+        assert_eq!("2010-07-01T07:00:00.123-04:00", result.value(1));
+        assert!(result.is_null(2));
+
+        let to_type = DataType::Timestamp(TimeUnit::Nanosecond, None);
+        let timestamp_array = cast(&timestamp_array, &to_type).unwrap();
+
+        let string_array = cast(&timestamp_array, &DataType::Utf8).unwrap();
+        let result = 
string_array.as_any().downcast_ref::<StringArray>().unwrap();
+        assert_eq!("2000-01-01T12:00:00.123", result.value(0));

Review Comment:
   Let me think about this a bit more. I was thinking that when someone try to 
cast Some(tz) -> None, they probably want to cast to UTC.



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