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Posted to issues@arrow.apache.org by "dangotbanned (via GitHub)" <gi...@apache.org> on 2025/12/04 22:28:20 UTC

[I] `pa.Table.from_struct_array` fails for an empty array [arrow]

dangotbanned opened a new issue, #48344:
URL: https://github.com/apache/arrow/issues/48344

   ### Describe the bug, including details regarding any error messages, version, and platform.
   
   This is the inverse of #46355, so I'll continue from there 😅:
   
   ### Repro
   
   ```py
   import pyarrow as pa
   
   table = pa.table({"a": pa.array([]), "b": pa.array([], type=pa.float64())})
   array = table.to_struct_array()
   
   print(array)
   print(array.type.fields)
   pa.Table.from_struct_array(array)
   ```
   
   ### Output
   
   ```py
   <pyarrow.lib.ChunkedArray object at 0x...>
   [
   
   ]
   [pyarrow.Field<a: null>, pyarrow.Field<b: double>]
   
   ./pyarrow/table.pxi:4945, in pyarrow.lib.Table.from_struct_array()
   
   ./pyarrow/table.pxi:5032, in pyarrow.lib.Table.from_batches()
   
   ValueError: Must pass schema, or at least one RecordBatch
   ```
   
   ### Workaround
   I'm doing quite a lot of version branching here already:
   - https://github.com/narwhals-dev/narwhals/blob/e4f0f83a15808349f2f4970e5549b791671fe601/narwhals/_plan/arrow/series.py#L321-L330
   - https://github.com/narwhals-dev/narwhals/blob/e4f0f83a15808349f2f4970e5549b791671fe601/narwhals/_plan/arrow/functions.py#L337-L334
   
   In short, it looks like:
   
   ```py
   import pyarrow as pa
   
   table = pa.table({"a": pa.array([]), "b": pa.array([], type=pa.float64())})
   array = table.to_struct_array()
   
   from_struct_array = pa.schema(array.type.fields).empty_table()
   print(from_struct_array)
   ```
   
   ```py
   pyarrow.Table
   a: null
   b: double
   ----
   a: [0 nulls]
   b: [[]]
   ```
   
   ### Component(s)
   
   Python


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Re: [I] `pa.Table.from_struct_array` fails for an empty array [arrow]

Posted by "AlenkaF (via GitHub)" <gi...@apache.org>.
AlenkaF commented on issue #48344:
URL: https://github.com/apache/arrow/issues/48344#issuecomment-4766497214

   @1fanwang can you add a comment under this issue, so I can assign it to you?


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Re: [I] `pa.Table.from_struct_array` fails for an empty array [arrow]

Posted by "AlenkaF (via GitHub)" <gi...@apache.org>.
AlenkaF commented on issue #48344:
URL: https://github.com/apache/arrow/issues/48344#issuecomment-5448729704

   Issue resolved by pull request 49869
   https://github.com/apache/arrow/pull/49869


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Re: [I] `pa.Table.from_struct_array` fails for an empty array [arrow]

Posted by "1fanwang (via GitHub)" <gi...@apache.org>.
1fanwang commented on issue #48344:
URL: https://github.com/apache/arrow/issues/48344#issuecomment-4773565599

   > [@1fanwang](https://github.com/1fanwang) can you add a comment under this issue, so I can assign it to you?
   
   Thanks @AlenkaF 
   PR opened https://github.com/apache/arrow/pull/49869 to address this issue.


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Re: [I] `pa.Table.from_struct_array` fails for an empty array [arrow]

Posted by "AlenkaF (via GitHub)" <gi...@apache.org>.
AlenkaF closed issue #48344: `pa.Table.from_struct_array` fails for an empty array
URL: https://github.com/apache/arrow/issues/48344


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