[jira] [Created] (ARROW-7782) Losing index information when using write_to_dataset with partition_cols

["Ludwik Bielczynski (Jira)" <ji...@apache.org>]

Ludwik Bielczynski created ARROW-7782:
-----------------------------------------

             Summary: Losing index information when using write_to_dataset with partition_cols
                 Key: ARROW-7782
                 URL: https://issues.apache.org/jira/browse/ARROW-7782
             Project: Apache Arrow
          Issue Type: Bug
         Environment: pyarrow==0.15.1
            Reporter: Ludwik Bielczynski


One cannot save the index when using {{pyarrow.parquet.write_to_dataset()}} with given partition_cols arguments. Here I have created a minimal example which shows the issue:
{code:java}
 
from pathlib import Path
import pandas as pd
from pyarrow import Table
from pyarrow.parquet import write_to_dataset
path = Path('/home/ludwik/Documents/YieldPlanet/research/trials')
file_name = 'trial_pq.parquet'
df = pd.DataFrame({"A": [1, 2, 3], 
 "B": ['a', 'a', 'b']
 }, 
 index=pd.Index(['a', 'b', 'c'], name='idx'))

table = Table.from_pandas(df)
write_to_dataset(table, str(path / file_name), partition_cols=['B'],
 partition_filename_cb=None, filesystem=None)
{code}
 

The issue is rather important for pandas and dask users.



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