[GitHub] [arrow] seddonm1 commented on a change in pull request #8794: ARROW-10759: [Rust][DataFusion] Implement string to date cast

[GitBox <gi...@apache.org>]

seddonm1 commented on a change in pull request #8794:
URL: https://github.com/apache/arrow/pull/8794#discussion_r534498221



##########
File path: rust/arrow/src/compute/kernels/cast.rs
##########
@@ -376,6 +378,27 @@ pub fn cast(array: &ArrayRef, to_type: &DataType) -> Result<ArrayRef> {
             Int64 => cast_string_to_numeric::<Int64Type>(array),
             Float32 => cast_string_to_numeric::<Float32Type>(array),
             Float64 => cast_string_to_numeric::<Float64Type>(array),
+            Date32(DateUnit::Day) => {
+                use chrono::{NaiveDate, NaiveTime};
+                let zero_time = NaiveTime::from_hms(0, 0, 0);
+                let string_array = array.as_any().downcast_ref::<StringArray>().unwrap();
+                let mut builder = PrimitiveBuilder::<Date32Type>::new(string_array.len());
+                for i in 0..string_array.len() {
+                    if string_array.is_null(i) {
+                        builder.append_null()?;
+                    } else {
+                        match NaiveDate::parse_from_str(string_array.value(i), "%Y-%m-%d")
+                        {
+                            Ok(date) => builder.append_value(
+                                (date.and_time(zero_time).timestamp() / SECONDS_IN_DAY)
+                                    as i32,
+                            )?,
+                            Err(_) => builder.append_null()?, // not a valid date

Review comment:
       I know this has been merged but do you really want to append null and not inform user when a value cannot be correctly parsed? This is the behaviour of Spark but is very dangerous in some cases (especially dealing with money).




----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org