Re: [PR] MINOR: [Python][Parquet] Clarify code around restoring pandas metadata in ParquetDataset.read() [arrow]

["TomAugspurger (via GitHub)" <gi...@apache.org>]

TomAugspurger commented on PR #51151:
URL: https://github.com/apache/arrow/pull/51151#issuecomment-6084791916

   FYI @jorisvandenbossche, this did cause a behavior change in pandas when reading zero columns. With pyarrow==25.x, that returned a `(0, 0)` shape dataframe. With pyarrow==26, it returns a `(nrows, 0)` shape dataframe
   
   ```python
   import io
   
   import pandas as pd
   
   df = pd.DataFrame({"a": [1, 2, 3]})
   b = io.BytesIO()
   df.to_parquet(b)
   empty = pd.read_parquet(b, columns=[])
   print(empty.shape)  # (0, 0) for pyarrow=25.x; (3, 0) for pyarrow=26.x
   ```
   
   I think that `(nrows, 0)` is the shape I'd expect, but leaving a note here in case anyone else stumbles across this (xref https://github.com/NVIDIA/cudf/pull/24520).


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