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Author: jorisvandenbossche

pandas/core/array_algos/masked_reductions.py

@@ -63,6 +63,7 @@ def _reductions(
             return libmissing.NA
 
         if values.dtype == np.dtype(object):
+            # object dtype does not support `where` without passing an initial
             values = values[~mask]
             return func(values, axis=axis, **kwargs)
         return func(values, where=~mask, axis=axis, **kwargs)

pandas/core/arrays/arrow/array.py

@@ -1730,6 +1730,7 @@ def pyarrow_meth(data, skip_nulls, min_count=0):
                         return pa.scalar(None, type=data.type)
 
                 if pa.types.is_large_string(data.type):
+                    # binary_join only supports string, not large_string
                     data = data.cast(pa.string())
                 data_list = pa.ListArray.from_arrays(
                     [0, len(data)], data.combine_chunks()