[jira] [Commented] (ARROW-13151) [Python] Unable to read single child field of struct column from Parquet

["Micah Kornfield (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-13151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17374935#comment-17374935 ] 

Micah Kornfield commented on ARROW-13151:
-----------------------------------------

{quote}As a side-note, if you do change the ugly "list.item" access
{quote}
Yeah this would be a seperate change, and I think we could make it be backwards compatible.    This would be a separate issue.  The reason why removing list.item makes sense is that there are legacy encodings that encode lists in different ways, it would be nice to have a uniform access to these different types (i.e. schema evolution), I'll open up a separate item to track this and we can have more discussion there, I don't expect anyone would take this up any time soon.

> [Python] Unable to read single child field of struct column from Parquet
> ------------------------------------------------------------------------
>
>                 Key: ARROW-13151
>                 URL: https://issues.apache.org/jira/browse/ARROW-13151
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Parquet, Python
>            Reporter: Angus Hollands
>            Priority: Major
>
> Given the following table
> {code:java}
> data = {"root": [[{"addr": {"this": 3, "that": 3}}]]}
> table = pa.Table.from_pydict(data)
> {code}
> reading the nested column leads to an {{pyarrow.lib.ArrowInvalid}} error:
> {code:java}
> pq.write_table(table, "/tmp/table.parquet")
> file = pq.ParquetFile("/tmp/table.parquet")
> array = file.read(["root.list.item.addr.that"])
> {code}
> Traceback:
> {code:java}
> Traceback (most recent call last):
>   File "....", line 21, in <module>
>     array = file.read(["root.list.item.addr.that"])
>   File "/home/angus/.mambaforge/envs/awkward/lib/python3.9/site-packages/pyarrow/parquet.py", line 383, in read
>     return self.reader.read_all(column_indices=column_indices,
>   File "pyarrow/_parquet.pyx", line 1097, in pyarrow._parquet.ParquetReader.read_all
>   File "pyarrow/error.pxi", line 97, in pyarrow.lib.check_status
> pyarrow.lib.ArrowInvalid: List child array invalid: Invalid: Struct child array #0 does not match type field: struct<that: int64> vs struct<that: int64, this: int64>
> {code}
> It's possible that I don't quite understand this properly - am I doing something wrong?



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