[C++] cumulative_sum ignores CumulativeSumOptions::check_overflow #35789
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pitrou
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Jun 1, 2023
### Rationale for this change
There are two variants of cumsum, `cumulative_sum` always wraps around on overflow and `cumulative_sum_checked` always return `Status::Invalid` on overflow, regardless of the `check_overflow` parameter in CumulativeSumOptions.
For example:
```cpp
CumulativeSumOptions options(/*start=*/0, /*skip_nulls=*/true, /*check_overflow=*/true);
auto res = CallFunction("cumulative_sum", {ArrayFromJSON(int8(), "[127, 1]")}, &options);
std::cout << res->make_array()->ToString() << std::endl;
// prints [127, -128], but user might expect an error returned.
```
I believe it's more of a ambiguity rather than a bug. The document of `cumulative_sum` also doesn't mention `check_overflow` at all, and `check_overflow` is not exposed to pyarrow. So IMO the best approach to avoid confusion is to remove `check_overflow` from CumulativeSumOptions.
The only place where `check_overflow` is used is in the C++ convenience function `CumulativeSum` defined in api_vector.h, which calls `cumulative_sum_checked` or `cumulative_sum` depending on the parameter. It can be replaced by a bool parameter in the C++ convenience function.
### What changes are included in this PR?
1. `check_overflow` is removed from CumulativeSumOptions.
2. Add a bool check_overflow parameter to the C++ convenience function CumulativeSum.
### Are these changes tested?
It doesn't affect the current tests.
### Are there any user-facing changes?
Yes, but only the C++ convenience function because check_overflow is not used in the kernel implementation and not exposed to pyarrow anyways.
* Closes: #35789
Authored-by: Jin Shang <shangjin1997@gmail.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>
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Describe the bug, including details regarding any error messages, version, and platform.
There are two variants of cumsum,
cumulative_sumalways wraps around on overflow andcumulative_sumalways returnStatus::Invalidon overflow, regardless of thecheck_overflowparameter in CumulativeSumOptions.For example:
I believe it's more of a ambiguity rather than a bug. The document of
cumulative_sumalso doesn't memtioncheck_overflowat all, andcheck_overflowis not exposed to pyarrow. So IMO the best approach to avoid confusion is to removecheck_overflowfrom CumulativeSumOptions.The only place where
check_overflowis used is in the convenience functionCumulativeSumdefined in api_vector.h, which callscumulative_sum_checkedorcumulative_sumdepending on the parameter. It can be replaced by a bool parameter in the convenience function.Component(s)
C++
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