Add comparison kernels for BinaryArray

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Currently there is no support for comparing BinaryArray

Describe the solution you'd like

It should be possible to call arrow::compute::eq_dyn, and friends with BinaryArray as arguments and have them not return an error. It may be possible to share code with the existing utf8 implementation.

Additional context

Encountered whilst implementing #1053

[alamb]

This is a pretty good ticket for anyone who wants to mess with the compute kernels -- basically it should be add a small amount of code and a a test

[HaoYang670]

Hi Raphael, I am newcomer and want to contribute to this project.
Is it reasonable to add a function called eq_dyn_binary_scalar and tests in the file comparison.rs?

[tustvold]

Yes it should be largely just a case of adding _binary versions of the _utf8 kernels in that module.

Typically there are three variants of each operator:

• One with fully qualified array types e.g. lt_eq_utf8
• One with a fully quality array type and a scalar e.g. lt_eq_utf8_scalar
• One with a dynamic array type and qualified scalar e.g. lt_eq_dyn_utf8_scalar

Finally there are then two dynamic dispatch functions for each operator

• One that takes two dynamic array types - e.g. lt_eq_dyn (the dispatch logic is macro-ified)
• One that takes a dynamic array and a scalar - e.g. lt_eq_dyn_scalar (this doesn't support non-primitive types AFAICT)

I'd perhaps recommend starting with the fully qualified kernels and build up from there with successive PRs. The scalar variants are also optimisations and so could definitely be ignored for an initial cut, they were only added in the last month 😀

[HaoYang670]

Thank you, Raphael! I'd like to try if no one else has been doing it.

[HaoYang670]

Following your advice, I will file 2 PRs to match this feature. The first PR will add support for fully qualified binary array. The second PR will support comparison for dynamic binary array.

[HaoYang670]

Is there something like BinaryDictionaryBuilder in the code, which is needed when testing the eq_dyn_binary_scalar_with_dict?

[HaoYang670]

BTW, could you please assign this issue to me?
I have no right to self-assign.

[alamb]

Is there something like BinaryDictionaryBuilder in the code, which is needed when testing the eq_dyn_binary_scalar_with_dict?

I do not know of any such thing, sadly

[HaoYang670]

I do not include DictionaryArray in my PR, because I do not find a straight forward way to build a binary dictionary. If it is needed, I will include it later in my PR.