TomAugspurger opened a new issue, #47177:
URL: https://github.com/apache/arrow/issues/47177
### Describe the bug, including details regarding any error messages,
version, and platform.
When using `pyarrow.dataset.dataset` to read a partitioned parquet dataset
that's partitioned on a `large_string` field, I see a `ArrowTypeError: Unable
to merge: Field part has incompatible types: large_string vs string`:
```python
import pyarrow as pa
import pyarrow.dataset
import pathlib
import pyarrow.parquet
t = pa.table(
{"part": pa.array(["a", "a", "b", "b"], type=pa.large_string()), "col":
[1, 2, 3, 4]}
)
root = pathlib.Path("string.parquet")
a = root / "a/data.parquet"
b = root / "b/data.parquet"
a.parent.mkdir(parents=True, exist_ok=True)
b.parent.mkdir(parents=True, exist_ok=True)
pyarrow.parquet.write_table(t[:2], a)
pyarrow.parquet.write_table(t[2:], b)
source = list(root.glob("**/*.parquet"))
t = pyarrow.dataset.dataset(root, partitioning=["part"],
partition_base_dir=str(root))
```
errors with
```pytb
Traceback (most recent call last):
File "/Users/toaugspurger/gh/dask/dask/debug.py", line 21, in <module>
t = pyarrow.dataset.dataset(root, partitioning=["part"],
partition_base_dir=str(root))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File
"/Users/toaugspurger/gh/dask/.venv/lib/python3.12/site-packages/pyarrow/dataset.py",
line 790, in dataset
return _filesystem_dataset(source, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File
"/Users/toaugspurger/gh/dask/.venv/lib/python3.12/site-packages/pyarrow/dataset.py",
line 482, in _filesystem_dataset
return factory.finish(schema)
^^^^^^^^^^^^^^^^^^^^^^
File "pyarrow/_dataset.pyx", line 3196, in
pyarrow._dataset.DatasetFactory.finish
File "pyarrow/error.pxi", line 155, in
pyarrow.lib.pyarrow_internal_check_status
File "pyarrow/error.pxi", line 92, in pyarrow.lib.check_status
pyarrow.lib.ArrowTypeError: Unable to merge: Field part has incompatible
types: large_string vs string
```
I don't observe that failure with `type=pa.string()`, just `large_string()`.
### Component(s)
C++, Python
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