[GitHub] [arrow-rs] tustvold commented on a diff in pull request #2169: Use ArrayAccessor and FromIterator in Cast Kernels

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

tustvold commented on code in PR #2169:
URL: https://github.com/apache/arrow-rs/pull/2169#discussion_r930099724


##########
arrow/src/compute/kernels/cast.rs:
##########
@@ -270,45 +269,62 @@ pub fn cast(array: &ArrayRef, to_type: &DataType) -> Result<ArrayRef> {
     cast_with_options(array, to_type, &DEFAULT_CAST_OPTIONS)
 }
 
-// cast the integer array to defined decimal data type array
-macro_rules! cast_integer_to_decimal {
-    ($ARRAY: expr, $ARRAY_TYPE: ident, $PRECISION : ident, $SCALE : ident) => {{
-        let array = $ARRAY.as_any().downcast_ref::<$ARRAY_TYPE>().unwrap();
-        let mul: i128 = 10_i128.pow(*$SCALE as u32);
-        let decimal_array = array
-            .iter()
-            .map(|v| {
-                v.map(|v| {
-                    let v = v as i128;
-                    // with_precision_and_scale validates the
-                    // value is within range for the output precision
-                    mul * v
-                })
-            })
-            .collect::<Decimal128Array>()
-            .with_precision_and_scale(*$PRECISION, *$SCALE)?;
-        Ok(Arc::new(decimal_array))
-    }};
+/// Cast the primitive array to defined decimal data type array
+fn cast_primitive_to_decimal<T: ArrayAccessor, F>(
+    array: T,
+    op: F,
+    precision: usize,
+    scale: usize,
+) -> Result<Arc<dyn Array>>
+where
+    F: Fn(T::Item) -> i128,
+{
+    #[allow(clippy::redundant_closure)]
+    let decimal_array = ArrayIter::new(array)
+        .map(|v| v.map(|v| op(v)))
+        .collect::<Decimal128Array>()
+        .with_precision_and_scale(precision, scale)?;
+
+    Ok(Arc::new(decimal_array))
 }
 
-// cast the floating-point array to defined decimal data type array
-macro_rules! cast_floating_point_to_decimal {
-    ($ARRAY: expr, $ARRAY_TYPE: ident, $PRECISION : ident, $SCALE : ident) => {{
-        let array = $ARRAY.as_any().downcast_ref::<$ARRAY_TYPE>().unwrap();
-        let mul = 10_f64.powi(*$SCALE as i32);
-        let decimal_array = array
-            .iter()
-            .map(|v| {
-                v.map(|v| {
-                    // with_precision_and_scale validates the
-                    // value is within range for the output precision
-                    ((v as f64) * mul) as i128
-                })
-            })
-            .collect::<Decimal128Array>()
-            .with_precision_and_scale(*$PRECISION, *$SCALE)?;
-        Ok(Arc::new(decimal_array))
-    }};
+fn cast_integer_to_decimal<T: ArrowNumericType>(
+    array: &PrimitiveArray<T>,
+    precision: usize,
+    scale: usize,
+) -> Result<Arc<dyn Array>> {
+    let mul: i128 = 10_i128.pow(scale as u32);
+
+    // with_precision_and_scale validates the
+    // value is within range for the output precision
+    cast_primitive_to_decimal(
+        array,
+        |v| v.to_isize().unwrap() as i128 * mul,
+        precision,
+        scale,
+    )
+}
+
+fn cast_floating_point_to_decimal<T: ArrowNumericType>(
+    array: &PrimitiveArray<T>,
+    precision: usize,
+    scale: usize,
+) -> Result<Arc<dyn Array>>
+where
+    <T as ArrowPrimitiveType>::Native: ToPrimitive,
+{
+    let mul = 10_f64.powi(scale as i32);
+
+    cast_primitive_to_decimal(
+        array,
+        |v| {
+            // with_precision_and_scale validates the
+            // value is within range for the output precision
+            ((num::ToPrimitive::to_f64(&v).unwrap()) * mul) as i128

Review Comment:
   I think this is now a checked conversion where previously it wasn't?



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