[jira] [Commented] (ARROW-9078) [C++] Parquet writing of extension type with nested storage type fails

["Antoine Pitrou (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-9078?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17191829#comment-17191829 ] 

Antoine Pitrou commented on ARROW-9078:
---------------------------------------

Fixing the writing side is relatively easy, but the reading side looks like a can of worms.

> [C++] Parquet writing of extension type with nested storage type fails
> ----------------------------------------------------------------------
>
>                 Key: ARROW-9078
>                 URL: https://issues.apache.org/jira/browse/ARROW-9078
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Joris Van den Bossche
>            Assignee: Antoine Pitrou
>            Priority: Major
>              Labels: parquet
>             Fix For: 2.0.0
>
>
> A reproducer in Python:
> {code:python}
> import pyarrow as pa
> import pyarrow.parquet as pq
> class MyStructType(pa.PyExtensionType): 
>  
>     def __init__(self): 
>         pa.PyExtensionType.__init__(self, pa.struct([('left', pa.int64()), ('right', pa.int64())])) 
>  
>     def __reduce__(self): 
>         return MyStructType, () 
> struct_array = pa.StructArray.from_arrays(
>     [
>         pa.array([0, 1], type="int64", from_pandas=True),
>         pa.array([1, 2], type="int64", from_pandas=True),
>     ],
>     names=["left", "right"],
> )
> # works
> table = pa.table({'a': struct_array})
> pq.write_table(table, "test_struct.parquet")
> # doesn't work
> mystruct_array = pa.ExtensionArray.from_storage(MyStructType(), struct_array)
> table = pa.table({'a': mystruct_array})
> pq.write_table(table, "test_struct.parquet")
> {code}
> Writing the simple StructArray nowadays works (and reading it back in as well). 
> But when the struct array is the storage array of an ExtensionType, it fails with the following error:
> {code}
> ArrowException: Unknown error: data type leaf_count != builder_leaf_count1 2
> {code}



--
This message was sent by Atlassian Jira
(v8.3.4#803005)