[jira] [Commented] (ARROW-15270) [Python] Make dataset.dataset() accept a list of directories as source

["Will Jones (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-15270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17469991#comment-17469991 ] 

Will Jones commented on ARROW-15270:
------------------------------------

The current way to filter the partitions is to use the {{filter}} parameter in {{to_table}}. See: https://arrow.apache.org/docs/python/dataset.html#filtering-data

{code:python}
ds.dataset(source="partitioned", format="ipc")\
  .to_table(filter=(ds.field("year") == 2001) | (ds.field("year") == 2002))
{code}

Would that work for you?

> [Python] Make dataset.dataset() accept a list of directories as source
> ----------------------------------------------------------------------
>
>                 Key: ARROW-15270
>                 URL: https://issues.apache.org/jira/browse/ARROW-15270
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Python
>            Reporter: Reynaldo Rojas Zelaya
>            Priority: Major
>
> Currently, if I partition a dataset as shown below, a directory {{partitioned}} is created along with {{2001, 2002, 2003, 2004}} as subdirectories. But then, if I wanted to only read the partitions corresponding to years {{{}2001, 2002{}}}, I wouldn't have a straightforward way of doing so.
> {code:python}
> >>> table = pa.table({'month': [1, 2, 3, 4, 5], 'year': [2001, 2002, 2003, 2004, 2004]})
> >>> table
> pyarrow.Table
> month: int64
> year: int64
> ----
> month: [[1,2,3,4,5]]
> year: [[2001,2002,2003,2004,2004]]
> >>> ds.write_dataset(data=table, base_dir="partitioned", format="ipc", partitioning=ds.partitioning(pa.schema([("year", pa.int64())])))
> >>> f = fs.SubTreeFileSystem(base_path='partitioned', base_fs=fs.LocalFileSystem())
> >>> ds.dataset(source=['2001','2002'], filesystem=f, format="ipc")
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/Users/userr2232/Documents/misc/first-julia-nn/lib/python3.9/site-packages/pyarrow/dataset.py", line 683, in dataset
>     return _filesystem_dataset(source, **kwargs)
>   File "/Users/userr2232/Documents/misc/first-julia-nn/lib/python3.9/site-packages/pyarrow/dataset.py", line 423, in _filesystem_dataset
>     fs, paths_or_selector = _ensure_multiple_sources(source, filesystem)
>   File "/Users/userr2232/Documents/misc/first-julia-nn/lib/python3.9/site-packages/pyarrow/dataset.py", line 344, in _ensure_multiple_sources
>     raise IsADirectoryError(
> IsADirectoryError: Path 2001 points to a directory, but only file paths are supported. To construct a nested or union dataset pass a list of dataset objects instead.{code}
> Since {{dataset.write_dataset()}} produces this file structure, maybe {{dataset.dataset()}} should accept a list of directories as {{source}}?
>  



--
This message was sent by Atlassian Jira
(v8.20.1#820001)