[C++] Implement casts from one struct type to another (with same field names and number of fields)

[asfimport]

Reporter: Wes McKinney / @wesm
Assignee: Will Ayd / @WillAyd

Related issues:

• [C++] C++ array kernels framework and execution buildout (umbrella issue) (is a child of)
• [C++] Kernel to select subset of fields of a StructArray (is related to)

PRs and other links:

• GitHub Pull Request #12248

_{Note: This issue was originally created as ARROW-1888. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
This should be implemented in scalar_cast_nested.cc

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
Small example of what could be supported:

>>> arr = pa.array([{'a': 1, 'b': None}, {'a': 2, 'b': None}])
>>> arr.type
StructType(struct<a: int64, b: null>)

>>> arr.cast(pa.struct([('a', pa.int64()), ('b', pa.int64())]))
...
ArrowNotImplementedError: Unsupported cast from struct<a: int64, b: null> to struct using function cast_struct
../src/arrow/compute/function.cc:175  DispatchBest(&inputs)

[asfimport]

Antoine Pitrou / @pitrou:
cc @lidavidm

[asfimport]

Antoine Pitrou / @pitrou:
@diegodfrf Are you still planning to work on this?

[asfimport]

Will Ayd / @WillAyd:
I can take a look at this if it is still open

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
@WillAyd That would certainly be welcome!

[asfimport]

David Li / @lidavidm:
Issue resolved by pull request 12248
#12248