Dima Ryazanov created ARROW-1940: ------------------------------------ Summary: [Python] Extra metadata gets added after multiple conversions between pd.DataFrame and pa.Table Key: ARROW-1940 URL: https://issues.apache.org/jira/browse/ARROW-1940 Project: Apache Arrow Issue Type: Bug Components: Python Affects Versions: 0.8.0 Reporter: Dima Ryazanov Priority: Minor Attachments: fail.py
We have a unit test that verifies that loading a dataframe from a .parq file and saving it back with no changes produces the same result as the original file. It started failing with pyarrow 0.8.0. After digging into it, I discovered that after the first conversion from pd.DataFrame to pa.Table, the table contains the following metadata (among other things): {code} "column_indexes": [{"metadata": null, "field_name": null, "name": null, "numpy_type": "object", "pandas_type": "bytes"}] {code} However, after converting it to pd.DataFrame and back into a pa.Table for the second time, the metadata gets an encoding field: {code} "column_indexes": [{"metadata": {"encoding": "UTF-8"}, "field_name": null, "name": null, "numpy_type": "object", "pandas_type": "unicode"}] {code} See the attached file for a test case. So specifically, it appears that dataframe->table->dataframe->table conversion produces a different result from just dataframe->table - which I think is unexpected. -- This message was sent by Atlassian JIRA (v6.4.14#64029)