[jira] [Updated] (ARROW-8729) [C++][Dataset] Only selecting a partition column results in empty table

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-8729?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ASF GitHub Bot updated ARROW-8729:
----------------------------------
    Labels: dataset dataset-dask-integration pull-request-available  (was: dataset dataset-dask-integration)

> [C++][Dataset] Only selecting a partition column results in empty table
> -----------------------------------------------------------------------
>
>                 Key: ARROW-8729
>                 URL: https://issues.apache.org/jira/browse/ARROW-8729
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++
>            Reporter: Joris Van den Bossche
>            Assignee: Ben Kietzman
>            Priority: Major
>              Labels: dataset, dataset-dask-integration, pull-request-available
>             Fix For: 1.0.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Python reproducer:
> {code}
> import pyarrow as pa
> import pyarrow.parquet as pq
> import pyarrow.dataset as ds
> path = "test_dataset"
> table = pa.table({'part': ['a', 'a', 'b', 'b'], 'col': [1, 2, 3, 4]})
> pq.write_to_dataset(table, str(path), partition_cols=["part"])
> {code}
> gives
> {code}
> In [38]: ds.dataset(str(path), partitioning="hive").to_table().num_rows                                                                                                                                            
> Out[38]: 4
> In [39]: ds.dataset(str(path), partitioning="hive").to_table(columns=["part"]).num_rows                                                                                                                            
> Out[39]: 0
> {code}
> The schema correctly only includes the "part" column, but there are no rows.
> cc [~bkietz]



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