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https://issues.apache.org/jira/browse/ARROW-4538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16789982#comment-16789982
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Wes McKinney commented on ARROW-4538:
-------------------------------------
Hm, I'm working on ARROW-1639 and there's some weird interactions here. I don't
think we should attempt to preserve pandas indexes through
{{write_to_dataset}}. I'll comment in the PR I'm about to put up
> [PYTHON] Remove index column from subschema in write_to_dataframe
> -----------------------------------------------------------------
>
> Key: ARROW-4538
> URL: https://issues.apache.org/jira/browse/ARROW-4538
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 0.12.0
> Reporter: Christian Thiel
> Assignee: Christian Thiel
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.13.0
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> When using {{pa.Table.from_pandas()}} with preserve_index=True and
> dataframe.index.name!=None the prefix {{__index_level_}} is not added to the
> respective schema name. This breaks {{write_to_dataset}} with active
> partition columns.
> {code}
> import pyarrow as pa
> import pyarrow.parquet as pq
> import os
> import shutil
> import pandas as pd
> import numpy as np
> PATH_PYARROW_MANUAL = '/tmp/pyarrow_manual.pa/'
> if os.path.exists(PATH_PYARROW_MANUAL):
> shutil.rmtree(PATH_PYARROW_MANUAL)
> os.mkdir(PATH_PYARROW_MANUAL)
> arrays = np.array([np.array([0, 1, 2]), np.array([3, 4]), np.nan, np.nan])
> df = pd.DataFrame([0, 0, 1, 1], columns=['partition_column'])
> df['arrays'] = pd.Series(arrays)
> df.index.name='ID'
> table = pa.Table.from_pandas(df, preserve_index=True)
> print(table.schema.names)
> pq.write_to_dataset(table, root_path=PATH_PYARROW_MANUAL,
> partition_cols=['partition_column'],
> preserve_index=True
> )
> {code}
> Removing {{df.index.name='ID'}} works. Also disabling {{partition_cols}} in
> {{write_to_dataset}} works.
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