[jira] [Created] (ARROW-17174) FileSystemDataset FilenamePartitioning error - fsspec filesystem

["Adam Kirby (Jira)" <ji...@apache.org>]

Adam Kirby created ARROW-17174:
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             Summary: FileSystemDataset FilenamePartitioning error - fsspec filesystem
                 Key: ARROW-17174
                 URL: https://issues.apache.org/jira/browse/ARROW-17174
             Project: Apache Arrow
          Issue Type: Bug
          Components: C++, Python
    Affects Versions: 8.0.1
            Reporter: Adam Kirby
         Attachments: zip_of_csvs_test.py

Unless this is user error (which it may well be!), it seems that Dataset FilenamePartitioning on read doesn't seem to work with an fsspec filesystem. From what I can glean, the filenames can be parsed successfully when passed to the parse() method, but do not seem to be being extracted as fields from the filenames passed to dataset() – instead, they appear as nulls. When trying to use the partitioning discover() method (assuming this is a reasonable thing to try), I get the below traceback. (Repro python script attached).

Traceback (most recent call last):
  File "/zip_of_csvs_test.py", line 82, in <module>
    ds_partitioned = pds.dataset(
  File "/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pyarrow/dataset.py", line 697, in dataset
    return _filesystem_dataset(source, **kwargs)
  File "/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pyarrow/dataset.py", line 449, in _filesystem_dataset
    return factory.finish(schema)
  File "pyarrow/_dataset.pyx", line 1857, in pyarrow._dataset.DatasetFactory.finish
  File "pyarrow/error.pxi", line 144, in pyarrow.lib.pyarrow_internal_check_status
  File "pyarrow/error.pxi", line 100, in pyarrow.lib.check_status
pyarrow.lib.ArrowInvalid: No non-null segments were available for field 'frequency'; couldn't infer type



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