viirya commented on code in PR #3690:
URL: https://github.com/apache/arrow-rs/pull/3690#discussion_r1136410537
##########
arrow-arith/src/arithmetic.rs:
##########
@@ -1165,6 +1167,77 @@ pub fn multiply_dyn_checked(
}
}
+/// Perform `left * right` operation on two decimal arrays. If either left or
right value is
+/// null then the result is also null.
+///
+/// This performs decimal multiplication which allows precision loss if an
exact representation
+/// is not possible for the result, according to the required scale. In the
case, the result
+/// will be rounded to the required scale.
+///
+/// It is implemented for compatibility with precision loss `multiply`
function provided by
+/// other data processing engines. For multiplication with precision loss
detection, use
+/// `multiply` or `multiply_checked` instead.
+pub fn mul_fixed_point_checked(
+ left: &PrimitiveArray<Decimal128Type>,
+ right: &PrimitiveArray<Decimal128Type>,
+ required_scale: i8,
+) -> Result<ArrayRef, ArrowError> {
+ let precision = left.precision();
+ let product_scale = left.scale() + right.scale();
+
+ try_binary::<_, _, _, Decimal128Type>(left, right, |a, b| {
+ let a = i256::from_i128(a);
+ let b = i256::from_i128(b);
+
+ a.checked_mul(b)
+ .map(|mut a| {
+ if required_scale < product_scale {
Review Comment:
Returning an error for that.
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