[jira] [Updated] (ARROW-17360) [Python] pyarrow.orc.ORCFile.read does not preserve ordering of columns

["Joris Van den Bossche (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-17360?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Joris Van den Bossche updated ARROW-17360:
------------------------------------------
    Labels: orc  (was: )

> [Python] pyarrow.orc.ORCFile.read does not preserve ordering of columns
> -----------------------------------------------------------------------
>
>                 Key: ARROW-17360
>                 URL: https://issues.apache.org/jira/browse/ARROW-17360
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Python
>    Affects Versions: 8.0.1
>            Reporter: Matthew Roeschke
>            Priority: Major
>              Labels: orc
>
> xref [https://github.com/pandas-dev/pandas/issues/47944]
>  
> {code:java}
> In [1]: df = pd.DataFrame({"a": [1, 2, 3], "b": ["a", "b", "c"]})
> # pandas main branch / 1.5
> In [2]: df.to_orc("abc")
> In [3]: pd.read_orc("abc", columns=['b', 'a'])
> Out[3]:
>    a  b
> 0  1  a
> 1  2  b
> 2  3  c
> In [4]: import pyarrow.orc as orc
> In [5]: orc_file = orc.ORCFile("abc")
> # reordered to a, b
> In [6]: orc_file.read(columns=['b', 'a']).to_pandas()
> Out[6]:
>    a  b
> 0  1  a
> 1  2  b
> 2  3  c
> # reordered to a, b
> In [7]: orc_file.read(columns=['b', 'a'])
> Out[7]:
> pyarrow.Table
> a: int64
> b: string
> ----
> a: [[1,2,3]]
> b: [["a","b","c"]] {code}



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