rluvaton commented on code in PR #8653:
URL: https://github.com/apache/arrow-rs/pull/8653#discussion_r2463799949
##########
arrow-select/src/zip.rs:
##########
@@ -166,9 +196,465 @@ pub fn zip(
Ok(make_array(data))
}
+/// Zipper for 2 scalars
+///
+/// Useful for using in `IF <expr> THEN <scalar> ELSE <scalar> END` expressions
+///
+/// # Example
+/// ```
+/// # use std::sync::Arc;
+/// # use arrow_array::{ArrayRef, BooleanArray, Int32Array, Scalar,
cast::AsArray, types::Int32Type};
+///
+/// # use arrow_select::zip::ScalarZipper;
+/// let scalar_truthy = Scalar::new(Int32Array::from_value(42, 1));
+/// let scalar_falsy = Scalar::new(Int32Array::from_value(123, 1));
+/// let zipper = ScalarZipper::try_new(&scalar_truthy, &scalar_falsy).unwrap();
+///
+/// // Later when we have a boolean mask
+/// let mask = BooleanArray::from(vec![true, false, true, false, true]);
+/// let result = zipper.zip(&mask).unwrap();
+/// let actual = result.as_primitive::<Int32Type>();
+/// let expected = Int32Array::from(vec![Some(42), Some(123), Some(42),
Some(123), Some(42)]);
+/// ```
+///
+#[derive(Debug, Clone)]
+pub struct ScalarZipper {
+ zip_impl: Arc<dyn ZipImpl>,
+}
+
+impl ScalarZipper {
+ /// Try to create a new ScalarZipper from two scalar Datum
+ ///
+ /// # Errors
+ /// returns error if:
+ /// - the two Datum have different data types
+ /// - either Datum is not a scalar (or has more than 1 element)
+ ///
+ pub fn try_new(truthy: &dyn Datum, falsy: &dyn Datum) -> Result<Self,
ArrowError> {
+ let (truthy, truthy_is_scalar) = truthy.get();
Review Comment:
wouldn't it complicate things for no real benefit since `Datum.get` is
**really** cheap
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