[GitHub] [arrow-datafusion] berkaysynnada commented on a diff in pull request #6196: feat: allow scalars to appear as the LHS arg in arithmetic operations on temporal values

["berkaysynnada (via GitHub)" <gi...@apache.org>]

berkaysynnada commented on code in PR #6196:
URL: https://github.com/apache/arrow-datafusion/pull/6196#discussion_r1183937192


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datafusion/physical-expr/src/expressions/datetime.rs:
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@@ -120,16 +120,21 @@ impl PhysicalExpr for DateTimeIntervalExpr {
             (ColumnarValue::Array(array_lhs), ColumnarValue::Scalar(array_rhs)) => {
                 resolve_temporal_op_scalar(&array_lhs, sign, &array_rhs)
             }
+            // This function evaluates operations between a scalar value and an array of temporal
+            // values. One example is calculating the duration between a scalar timestamp and an
+            // array of timestamps (i.e. `now() - some_column`).
+            (ColumnarValue::Scalar(scalar_lhs), ColumnarValue::Array(array_rhs)) => {
+                let array_lhs = scalar_lhs.to_array_of_size(array_rhs.len());
+                Ok(ColumnarValue::Array(resolve_temporal_op(

Review Comment:
   The purpose of the `resolve_temporal_op` is actually to work with real array types. Otherwise, would we need specialized handlers for scalar types? I think this case can be handled in two ways:
   1) `resolve_temporal_op_scalar` is extended with a commute parameter. This pattern is applied in `impl_op_arithmetic`. The same functions should be able to handle Scalar op Array and Array op Scalar.
   2) A similar resolve_temporal_op_scalar function can be added with replaced parameters of Array and Scalar.
   Thank you for working on this issue. I can assist further if needed.



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