[GitHub] [arrow-rs] alamb commented on a diff in pull request #2052: feat(compute): Support week0 (PostgreSQL behaviour) for temporal

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

alamb commented on code in PR #2052:
URL: https://github.com/apache/arrow-rs/pull/2052#discussion_r919932672


##########
arrow/src/compute/kernels/temporal.rs:
##########
@@ -112,31 +112,28 @@ macro_rules! return_compute_error_with {
     };
 }
 
-trait ChronoDateQuarter {
+// Internal trait, which is used for mapping values from DateLike structures
+trait ChronoDateExt {
     /// Returns a value in range `1..=4` indicating the quarter this date falls into
     fn quarter(&self) -> u32;
 
     /// Returns a value in range `0..=3` indicating the quarter (zero-based) this date falls into
     fn quarter0(&self) -> u32;
+
+    fn weekday0(&self) -> i32;

Review Comment:
   ```suggestion
       /// Returns the day of week; Sunday is encoded as `0`, Monday as `1`, etc.
       fn weekday0(&self) -> i32;
   ```



##########
arrow/src/compute/kernels/temporal.rs:
##########
@@ -298,6 +295,37 @@ where
     Ok(b.finish())
 }
 
+/// Extracts the day of week of a given temporal array as an array of
+/// integers.

Review Comment:
   ```suggestion
   /// integers, starting at Sunday. This is different than [`weekday`] which starts at Monday.
   ```



##########
arrow/src/compute/kernels/temporal.rs:
##########
@@ -112,31 +112,28 @@ macro_rules! return_compute_error_with {
     };
 }
 
-trait ChronoDateQuarter {
+// Internal trait, which is used for mapping values from DateLike structures
+trait ChronoDateExt {
     /// Returns a value in range `1..=4` indicating the quarter this date falls into
     fn quarter(&self) -> u32;
 
     /// Returns a value in range `0..=3` indicating the quarter (zero-based) this date falls into
     fn quarter0(&self) -> u32;
+
+    fn weekday0(&self) -> i32;
 }
 
-impl ChronoDateQuarter for NaiveDateTime {
+impl<T: Datelike> ChronoDateExt for T {
     fn quarter(&self) -> u32 {
         self.quarter0() + 1
     }
 
     fn quarter0(&self) -> u32 {
         self.month0() / 3
     }
-}
-
-impl ChronoDateQuarter for NaiveDate {
-    fn quarter(&self) -> u32 {
-        self.quarter0() + 1
-    }
 
-    fn quarter0(&self) -> u32 {
-        self.month0() / 3
+    fn weekday0(&self) -> i32 {
+        self.weekday().num_days_from_sunday() as i32

Review Comment:
   🤔  now I see that chrono uses the names `num_days_from_sunday` and `num_days_from_monday`
   
   https://docs.rs/chrono/0.4.19/chrono/enum.Weekday.html#method.num_days_from_sunday
   https://docs.rs/chrono/0.4.19/chrono/enum.Weekday.html#method.num_days_from_monday
   
   What would  you think about using those names instead of `weekday0` and `weekday` @ovr  (I would be happy to rename things in a follow on PR prior to release)?



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