Incorrect roundtrip of index names on filtered dataframe

When saving a filtered dataframe to parquet using Pandas and fastparquet the index names are round-tripped incorrectly: ​

import pandas  as pd 

df = pd._testing.makeMixedDataFrame()

filtered_df = df[df.A>=1]

filtered_df.to_parquet('test.parq', engine='fastparquet')

loaded_df = pd.read_parquet('test.parq')

print(filtered_df.index.names)
print(loaded_df.index.names)

FrozenList([None])
FrozenList(['index'])

Versions

fastparquet 0.7.2 pandas 1.3.2

[martindurant]

@yohplala , you are probably in a good place to ensure None roundtrips, if you have any interest. I can fix any tests that this causes to fail in Dask. I have the feeling the issue isn’t high priority.

[martindurant]

No rush! I might do it myself also, but I have a similar problem with finding time 😃