Pyarrow casting chunked array to string type yields ArrowCapacityError

[samster25]

Describe the bug, including details regarding any error messages, version, and platform.

Hello,

I'm hitting an issue when casting an integer ChunkedArray to a string type. The issue happens when the target array chunk size of the string array is too large. Instead of performing the cast at the granularity of the input chunks, pyarrow should do it based on the target array size.

arr = 9_999_999_999_999 * np.ones(1_000_000_000//8) # 1 GB Array

pa_arr = pa.chunked_array([arr])

pa_arr
<pyarrow.lib.ChunkedArray object at 0x16a1cfce0>
[
  [
    9.999999999999e+12,
    9.999999999999e+12,
    9.999999999999e+12,
    9.999999999999e+12,
    9.999999999999e+12,
    ...
    9.999999999999e+12,
    9.999999999999e+12,
    9.999999999999e+12,
    9.999999999999e+12,
    9.999999999999e+12
  ]
]

pa_arr.cast(pa.string())
---------------------------------------------------------------------------
ArrowCapacityError                        Traceback (most recent call last)
line 1
----> 1 pa_arr.cast(pa.string())

File ~/code/Daft/venv/lib/python3.11/site-packages/pyarrow/table.pxi:551, in pyarrow.lib.ChunkedArray.cast()

File ~/code/Daft/venv/lib/python3.11/site-packages/pyarrow/compute.py:400, in cast(arr, target_type, safe, options, memory_pool)
    398     else:
    399         options = CastOptions.safe(target_type)
--> 400 return call_function("cast", [arr], options, memory_pool)

File ~/code/Daft/venv/lib/python3.11/site-packages/pyarrow/_compute.pyx:572, in pyarrow._compute.call_function()

File ~/code/Daft/venv/lib/python3.11/site-packages/pyarrow/_compute.pyx:367, in pyarrow._compute.Function.call()

File ~/code/Daft/venv/lib/python3.11/site-packages/pyarrow/error.pxi:144, in pyarrow.lib.pyarrow_internal_check_status()

File ~/code/Daft/venv/lib/python3.11/site-packages/pyarrow/error.pxi:125, in pyarrow.lib.check_status()

ArrowCapacityError: array cannot contain more than 2147483646 bytes, have 2147483664

Component(s)

Python

[js8544]

An arrow StringArray cannot contain more than int32_max bytes in total because StringArray uses int32 to store the offsets. pa_arr.cast(pa.large_string()) works fine in your case.

Instead of performing the cast at the granularity of the input chunks, pyarrow should do it based on the target array size.

Sorry but I don't quite get this. Could you elaborate a bit?