feat(arrow-array): add BinaryArrayType similar to StringArrayType

[rluvaton]

Rationale for this change

This trait helps to abstract over the different types of binary arrays
so that we don't need to duplicate the implementation for each type.

Same as StringArrayType

What changes are included in this PR?

Added BinaryArrayType and implemented for BinaryArray, LargeBinaryArray, BinaryViewArray and FixedSizeBinaryArray

Are there any user-facing changes?

Yes, there is a new public trait

[wiedld]

Question. What does this provide which is missing with the current IntoIterator implementations for &'a GenericByteArray, &'a FixedSizeBinaryArray, and &'a BinaryViewArray?

[alamb]

Thanks @rluvaton and @wiedld -- this looks like a good idea to me.

My concern is that this code is untested.

Would it be possible to use of this trait somewhere(e.g rewrite one of the existing kernels using it)? That would be the best kind of test in my opinion

[wiedld]

Question. What does this provide which is missing with the current IntoIterator implementations for &'a GenericByteArray, &'a FixedSizeBinaryArray, and &'a BinaryViewArray?

My question above is because I think this may not be needed? But I wasn't sure if I was missing something.

This introduced trait converts a referenced array to an ArrayIter, and it does so by abstracting over these three generic types (GenericBinaryArray, BinaryViewArray, FixedSizeBinaryArray) calling the iter().

When I looked at the existing code, we have a &'a GenericByteArray which also takes a reference and returns ArrayIter. So I wasn't sure why this was needed -- and what it added by making the iter() trait which does the same thing as the existing into_iter() trait. Am I missing something?

[alamb]

When I looked at the existing code, we have a &'a GenericByteArray which also takes a reference and returns ArrayIter. So I wasn't sure why this was needed -- and what it added by making the iter() trait which does the same thing as the existing into_iter() trait. Am I missing something?

I am not sure -- that is why I was asking for an example of this trait being used -- then we can have a concrete discussion if this API is duplicative or not

[alamb]

When I looked at the existing code, we have a &'a GenericByteArray which also takes a reference and returns ArrayIter. So I wasn't sure why this was needed

I think the idea is that BinaryViewArray is not a GenericBinaryArray (it is a similarly named GenericBinaryViewArray, right?)

[kylebarron]

IMO this looks great.

I was just trying to figure out what this provided that ArrayAccessor didn't provide directly, and I didn't realize that ArrayAccessor only provided value and value_unchecked. So having this BinaryArrayType would be nicer to be able to use iterator methods over any generic binary array input.

    fn use_binary_array<'a>(array: impl arrow_array::ArrayAccessor<Item = &'a [u8]>) {
        // Have to manually iterate over the array
        for i in 0..array.len() {
            dbg!(String::from_utf8(array.value(i).to_vec()).unwrap());
        }
    }

    #[test]
    fn binary_array() {
        let mut builder = BinaryViewBuilder::new();
        builder.append_value(b"foo");
        builder.append_value(b"bar");
        builder.append_value(b"baz");
        use_binary_array(&builder.finish());

        let mut builder = FixedSizeBinaryBuilder::new(3);
        builder.append_value(b"foo").unwrap();
        builder.append_value(b"bar").unwrap();
        builder.append_value(b"baz").unwrap();
        use_binary_array(&builder.finish());
    }

[wiedld]

The above example use case (kindly provided by @kylebarron) -- is already passing on main. 🤔
See demonstration: influxdata#6.
I added comments for where the generic iterators are already implemented.

[alamb]

The above example use case (kindly provided by @kylebarron) -- is already passing on main. 🤔 See demonstration: influxdata#6. I added comments for where the generic iterators are already implemented.

So perhaps the conclusion is that ArrayAccessor is already sufficient, but it was not obvious / clear how to use it / find it.

What can we do to make it clearer to find? Maybe we can add this example on ArrayAccessor and then add a link to ArrayAccessor from the documentation for BinaryViewArray and BinaryArray and FixedSizdBinaryArray 🤔

[kylebarron]

Well, on the contrary I was saying that BinaryArrayType could be nice so that consumers could access iterator methods, instead of needing to iterate by hand. I'm not sure if that warrants a new public API, but given that StringArrayType already exists, I think having a binary corollary would make sense.