[Python] write_to_dataset, coerce_timestamps issue with stored binary schema #45062

Describe the bug, including details regarding any error messages, version, and platform.

When using coerce_timestamps=us, it seems that the parquet metadata are correclty being set as datetime[us] however, the stored binary arrow schema seems to still be a datetime[ns] creating mismatch of type depending on the engine you use to read the data.

import pandas as pd
import polars as pl
from pyarrow.parquet import ParquetFile, ParquetWriter


df = pd.DataFrame({"date": [pd.Timestamp.now()]})
df.to_parquet("us.parquet", coerce_timestamps="us", allow_truncated_timestamps=True, index=False)

pqf = ParquetFile("us.parquet")
writer = ParquetWriter("us_pyarrow.parquet", schema=pqf.schema.to_arrow_schema())
writer.write_table(pqf.read())
writer.close()


pl.read_parquet("us.parquet") # Gives datetime[ns]
pl.read_parquet("us_pyarrow.parquet") # Gives datetime[us]

ParquetFile("us.parquet").metadata.schema.to_arrow_schema() # gives datetime[us]
ParquetFile("us_pyarrow.parquet").metadata.schema.to_arrow_schema() # gives datetime[us]

Polars is probably leveraging the binary arrow schema stored in the metadata and therefore interpret the column as datetime[ns].

Running the following prevent the mismatch when using polars and we indeed get datetime[us]

df.to_parquet("us.parquet", coerce_timestamps="us", allow_truncated_timestamps=True, index=False, store_schema=False)

The issue is that store_schema is not supported in the write_to_dataset function as this parameter is not available in ParquetFileWriteOptions but only in the write_table function and ParquetWriter class.

Therefore, running the following doesn't work.

df.to_parquet("us.parquet", coerce_timestamps="us", allow_truncated_timestamps=True, index=False, store_schema=False, partition_cols=[])

I guess the stored binary arrow schema should be stored with datetime[us] instead of datetime[ns] when using coerce_timestamps parameter but the store_schema parameter should also be made available to the write_to_dataset function

Component(s)

Python