[jira] [Commented] (ARROW-10955) [C++] Reading empty json lists results in invalid non-nullable null type

["Peter Goldsborough (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-10955?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17253106#comment-17253106 ] 

Peter Goldsborough commented on ARROW-10955:
--------------------------------------------

Thanks for the response Joris. Two questions:
 # Is there a manual workaround we can use to make this conversion process still work? Like change the schema of the json table after it's been loaded?
 # When can we expect 3.0.0?

> [C++] Reading empty json lists results in invalid non-nullable null type
> ------------------------------------------------------------------------
>
>                 Key: ARROW-10955
>                 URL: https://issues.apache.org/jira/browse/ARROW-10955
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++, Python
>    Affects Versions: 0.17.0, 0.17.1, 1.0.0, 2.0.0
>         Environment: linux and mac
>            Reporter: Peter Goldsborough
>            Priority: Major
>              Labels: json
>             Fix For: 3.0.0
>
>
> We're using Arrow to convert from JSON to Parquet and occasionally have empty lists in our json. Reading such JSON into an Arrow table and writing it to Parquet currently fails. We noticed this issue in our C++ Arrow code, but it also happens from Python.
> Minimal repro:
> input.json:
> {"foo": []}
>  
> convert.py:
>  import pyarrow.json
>  import pyarrow.parquet
> t = pyarrow.json.read_json("input.json")
>  pyarrow.parquet.write_table(t, "out.parquet")
>   
> Produces:
> Traceback (most recent call last):
>  File "repro.py", line 5, in <module>
>  pyarrow.parquet.write_table(t, "out.parquet")
> env/lib/python3.8/site-packages/pyarrow/parquet.py", line 1717, in write_table
>  with ParquetWriter(
>  File "env/lib/python3.8/site-packages/pyarrow/parquet.py", line 554, in __init__
>  self.writer = _parquet.ParquetWriter(
>  File "pyarrow/_parquet.pyx", line 1409, in pyarrow._parquet.ParquetWriter.__cinit__
>  File "pyarrow/error.pxi", line 84, in pyarrow.lib.check_status
>  pyarrow.lib.ArrowInvalid: NullType Arrow field must be nullable
>  



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