Feature dyn Array::as_any_mut + Default implementation of arrays.

[ritchie46]

The new into_mut works like a charm. <3

But its quite hacky to make work with dyn Array.

We then need to use as_any() -> clone and drop the owned dyn Array to drop the ref count again.

Here an excerpt of what we do in polars:

        // Depending on the state of the underlying arrow array we
        // might be able to get a `MutablePrimitiveArray`
        //
        // This is only possible if the reference count of the array and its buffers are 1
        // So the logic below is needed to keep the reference count 1 if it is

        // First we must obtain an owned version of the array
        let arr = self.downcast_iter().next().unwrap();

        // increments 1
        let arr = arr.clone();

        // now we drop our owned ArrayRefs so that
        // decrements 1
        {
            self.chunks.clear();
        }

What I'd ideally like as an api would be:

let owned = std::mem::take(array.as_any_mut().downcast_mut::<PrimitiveArray<T>>())?;
owned.into_mut()

Then a Default implementation could be an empty array from that same type. This is similar to standard data collections in std.

Is this something we could add to the Array trait? I am willing to make a PR.

[declark1]

This would be great and was the exact issue I ran into and mentioned here. Thanks for sharing your solution, I will give this a try.

[jorgecarleitao]

I think that we have some challenges with the mutable versions since they are statically typed, while the arrays are dynamically typed.

Maybe it is time to introduce dynamically-typed mutable arrays that mimic 1-to-1 the current arrays?