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Phillip Cloud reassigned ARROW-1940: ------------------------------------ Assignee: Phillip Cloud > [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 > Assignee: Phillip Cloud > Priority: Minor > Fix For: 0.9.0 > > 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 (v7.6.3#76005)