Dandandan opened a new issue, #3645:
URL: https://github.com/apache/arrow-rs/issues/3645
**Describe the bug**
Multiplication for decimals is wrong for decimals
**To Reproduce**
<!--
Steps to reproduce the behavior:
-->
```
#[test]
fn test_decimal_multiplication() {
let a =
Decimal128Array::from_iter_values([1]).with_precision_and_scale(1, 1).unwrap();
let b =
Decimal128Array::from_iter_values([1]).with_precision_and_scale(1, 1).unwrap();
let e =
Decimal128Array::from_iter_values([1]).with_precision_and_scale(2, 2).unwrap();
let r = multiply(&a, &b).unwrap();
assert_eq!(e, r);
}
```
0.1 * 0.1 should return 0.01.
The current kernel just multiplies the raw integers but ignores the
scale/precision values of the.
```
left: `PrimitiveArray<Decimal128(2, 2)>
[
1,
]`,
right: `PrimitiveArray<Decimal128(38, 10)>
[
1,
]`', arrow-arith/src/arithmetic.rs:2958:9
```
**Expected behavior**
The kernel should add scale as well, values 0.1 * 0.1 should have primitive
value `1` with scale `2`.
**Additional context**
<!--
Add any other context about the problem here.
-->
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