ARROW-6772: [C++] Add operator== for interfaces with an Equals() method

[benibus]

Addresses ARROW-6772.

Adds util::EqualityComparable mixin to relevant types, replacing prior operator==() overloads if applicable.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-6772

[github-actions]

⚠️ Ticket has not been started in JIRA, please click 'Start Progress'.

[pitrou]

The RTools 40 mingw32 CI failure looked unrelated, so I restarted the job.

[benibus]

For reference, I've hacked together a list of potentially similar classes that may be worth inspecting - i.e. they declare Equals() but don't appear to inherit the mixin.

• arrow::Array
• arrow::Buffer
• arrow::ChunkedArray
• arrow::Datum
• arrow::KeyValueMetadata
• arrow::RecordBatch
• arrow::SparseCOOIndex
• arrow::SparseCSFIndex
• arrow::Table
• arrow::Tensor
• arrow::compute::ExecBatch
• arrow::compute::Expression
• arrow::compute::Forest
• arrow::compute::KernelSignature
• arrow::compute::TypeMatcher
• arrow::dataset::FileFormat
• arrow::flight::ActionType
• arrow::flight::FlightDescriptor
• arrow::flight::FlightEndpoint
• arrow::flight::Location
• arrow::flight::Ticket
• arrow::fs::FileSystem
• arrow::fs::GcsCredentials
• arrow::fs::GcsOptions
• arrow::fs::HdfsOptions
• arrow::fs::LocalFileSystemOptions
• arrow::ipc::Message

[pitrou]

For reference, I've hacked together a list of potentially similar classes that may be worth inspecting - i.e. they declare Equals() but don't appear to inherit the mixin.

Thanks @benibus . Looking at this list, many of these classes can have quite expensive equality (for example Array::Equals would compare the entire array contents), so I'm not sure it would be a good idea to add an implicit operator==. @bkietz What do you think?

[pitrou]

I'm gonna merge here since all is good. Thank you @benibus !

[ursabot]

Benchmark runs are scheduled for baseline = bc8a608 and contender = bda98aa. bda98aa 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 ⬇️0.37% ⬆️0.07%] test-mac-arm
[Failed ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.35% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] bda98aab ec2-t3-xlarge-us-east-2
[Finished] bda98aab test-mac-arm
[Failed] bda98aab ursa-i9-9960x
[Finished] bda98aab ursa-thinkcentre-m75q
[Finished] bc8a6082 ec2-t3-xlarge-us-east-2
[Finished] bc8a6082 test-mac-arm
[Failed] bc8a6082 ursa-i9-9960x
[Finished] bc8a6082 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