ARROW-15643: [C++] Allow selecting subset of fields of a StructArray via cast

[dhruv9vats]

Provide the ability to select a subset of the fields of a StructArray array by casting it to the required fields, provided the fields exist in the StructArray.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-15643

[dhruv9vats]

Currently, the output StructArray fields need to be in the same order as in the input StructArray and also have the same name.

[lidavidm]

LGTM, thanks. Do you want to mark this as ready now?

[dhruv9vats]

Would we have to address the other cases talked about in the JIRA in this PR itself, or will that involve follow-up PRs?

[lidavidm]

I think we can file a separate JIRA to handle reordering fields via a cast.

[ursabot]

Benchmark runs are scheduled for baseline = bda7087 and contender = ac3be08. ac3be08 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Finished ⬇️0.38% ⬆️0.0%] test-mac-arm
[Finished ⬇️1.07% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.34% ⬆️0.09%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ec2-t3-xlarge-us-east-2/builds/430|ac3be08e ec2-t3-xlarge-us-east-2>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-test-mac-arm/builds/415|ac3be08e test-mac-arm>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-i9-9960x/builds/415|ac3be08e ursa-i9-9960x>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-thinkcentre-m75q/builds/425|ac3be08e ursa-thinkcentre-m75q>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ec2-t3-xlarge-us-east-2/builds/429|bda70875 ec2-t3-xlarge-us-east-2>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-test-mac-arm/builds/414|bda70875 test-mac-arm>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-i9-9960x/builds/414|bda70875 ursa-i9-9960x>
[Finished] <https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-ursa-thinkcentre-m75q/builds/424|bda70875 ursa-thinkcentre-m75q>
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java

[jorisvandenbossche]

Are the follow-up JIRAs already created?

[lidavidm]

Thanks for the reminder Joris, filed ARROW-16112.

[jorisvandenbossche]

Thanks. Do we also still want to add a StructArray.select or alike as a more convenient way to do this for a single StructArray? (I can open an issue for that) Although in practice you will often deal with eg a ChunkedArray if it's coming from a Table, and then you don't have those type specific methods anyway.

[lidavidm]

We can probably still add it, though yeah, not sure how useful it is.