waynexia opened a new pull request, #6336:
URL: https://github.com/apache/arrow-rs/pull/6336
# Which issue does this PR close?
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Part of #3960
# Rationale for this change
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I find #3960 for the same reason -- tracking memory consumption with
`Array`s. The most straightforward way is to use the unstable `Allocator` API.
By adding a decoration layer to `Allocator` we can keep track of the
real-time memory consumption of each container instance. There is a tiny tool
that implements this https://github.com/waynexia/unkai
# What changes are included in this PR?
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The most important changes in this PR are
- add a feature gate `allocator_api`, same name as the unstable rust feature
- add an optional type parameter `A: Allocator = Global` to `MutableBuffer`
like `Vec`
Since this requires an unstable rust feature, `allocator_api` can only be
used in the nightly toolchain. To keep this library still working in the stable
toolchain when the feature gate is disabled, this PR defines many dummy structs
like `Global` and `Allocator` to substitute those from std lib as they are not
referencable without unstable feature.
When `allocator_api` is enabled, users can either appoint their `Allocator`
by new APIs `new_in` and `with_capacity_in` or invoking `From<Vec<T, A>>` which
will inherit the allocator from vec.
This PR is tested with MIRI:
```shell
cargo +nightly miri nextest run -p arrow-buffer -F allocator_api
cargo +nightly miri nextest run -p arrow-buffer
```
# Are there any user-facing changes?
New APIs as described above
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