[C++] Duplicate functions array_filter/array_take and filter/take

[asfimport]

This has been explained to me as a metafunction and a backend but in that case the backend should not be registered with the function registry. Note both:

const FunctionDoc filter_doc(
    "Filter with a boolean selection filter",
    ("The output is populated with values from the input at positions\n"
     "where the selection filter is non-zero.  Nulls in the selection filter\n"
     "are handled based on FilterOptions."),
    {"input", "selection_filter"}, "FilterOptions");

and

const FunctionDoc array_filter_doc(
    "Filter with a boolean selection filter",
    ("The output is populated with values from the input `array` at positions\n"
     "where the selection filter is non-zero.  Nulls in the selection filter\n"
     "are handled based on FilterOptions."),
    {"array", "selection_filter"}, "FilterOptions");

which seems wrong as well.

Also sort_indices / array_sort_indices

Reporter: Weston Pace / @westonpace

Related issues:

• [Python] Hide hash_* functions from pyarrow.compute (relates to)
• [Python][C++] index_in_meta_binary/is_in_meta_binary should not show up in functions list (relates to)

_{Note: This issue was originally created as ARROW-13873. Please see the migration documentation for further details.}

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
Specifically for the sort one: ArraySortOptions allows a nicer interface to specify the sort order, as you don't need to specify a "dummy" key as with SortOptions (pc.array_sort_indices(arr, order="ascending") vs pc.sort_indices(arr, sort_keys=[("dummy", "ascending")]).

(I don't know if that's worth enough to keep the separate kernel, though)

[asfimport]

Antoine Pitrou / @pitrou:
One problem is that there's no obvious way of deprecating a compute function in C++: we cannot emit a compile-time warning since the function is looked up at runtime.

[asfimport]

Antoine Pitrou / @pitrou:
We could:

1. mention the deprecation in the function doc

2. mention the deprecation in the function doc and add a flag to the function that bindings such as Python can use to emit a runtime Warning

3. do nothing and live with the slight redundancy