[jira] [Updated] (ARROW-5139) [Python/C++] Empty column selection no longer restores index

["Wes McKinney (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-5139?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney updated ARROW-5139:
--------------------------------
    Fix Version/s: 4.0.0

> [Python/C++] Empty column selection no longer restores index
> ------------------------------------------------------------
>
>                 Key: ARROW-5139
>                 URL: https://issues.apache.org/jira/browse/ARROW-5139
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++, Python
>    Affects Versions: 0.12.1
>            Reporter: Florian Jetter
>            Priority: Minor
>              Labels: parquet
>             Fix For: 4.0.0
>
>
> The index of a dataframe is no longer reconstructed when using empty column selection. This is a regression to 0.12.1 and probably only happens for pd.RangeIndex
> {code:python}
> import pandas as pd
> import pyarrow as pa
> import pyarrow.parquet as pq
> from kartothek.serialization import ParquetSerializer
> from storefact import get_store_from_url
> print(pa.__version__)
> df = pd.DataFrame(
>     {"a": [1, 2]}
> )
> print(df.index)
> table = pa.Table.from_pandas(df)
> buf = pa.BufferOutputStream()
> pq.write_table(table, buf)
> reader = pa.BufferReader(buf.getvalue().to_pybytes())
> table_restored = pq.read_pandas(reader, columns=[])
> df_restored = table_restored.to_pandas()
> print(len(df_restored))
> {code}



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