ZhangHuiGui opened a new issue, #41336:
URL: https://github.com/apache/arrow/issues/41336
### Describe the bug, including details regarding any error messages,
version, and platform.
It's an interesting problem we find recently in `case_when` kernel.
For the call function:
`CaseWhen({MakeStruct({cond1, cond2, cond3}), {arr1, arr2, arr3, arr4}})`
will produce the `case_when` logic like below:
```shell
cond1 --> arr1 decimal(9,7),
cond2 --> arr2 decimal(6,2),
cond3 --> arr3 decimal(3, 2),
arr4 decimal(2,1)
```
The `case_when` will use the `LastType` which is `decimal(2,1)` as it's
output type.
https://github.com/apache/arrow/blob/79799e59b1a0c7bde8b85ea955593b2d63d2a46c/cpp/src/arrow/compute/kernels/scalar_if_else.cc#L2683-L2685.
That means for the arr1/arr2/arr3's output results, the precision will be
set to `decimal(2,1)`, obviously it's inaccurate in fact especially when we the
`case_when` as an expression combining with aggregate's `sum/avg...`.
laotan332 [[email protected]](mailto:[email protected])
### Component(s)
C++
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