Hi Antoine, I agree. But my question is for Arrow StructArray with No null values. In this case, as per the documentation, n_buffers should be set to 0. However, “import_from_c” expects StructArray to always have at least 1 buffer allocated, otherwise it throws an exception.
Best, Hanqi > On Mar 4, 2022, at 8:47 AM, Antoine Pitrou <anto...@python.org> wrote: > > > Le 04/03/2022 à 04:17, Hanqi Wu a écrit : >> Hello community, >> As per the below documentation, for an Arrow StructArray, it won’t have any >> physical buffers backing it if it doesn’t contain any null value: >> https://arrow.apache.org/docs/format/Columnar.html#struct-layout However, in >> PyArrow, it complains if you try to import from C an ArrowArray representing >> Struct type without a null vector (no nulls), which, according to the Arrow >> spec above, is permitted. >> To be more detailed, when doing import from C, it expects the number of >> buffers to be 1, as coded here: >> https://github.com/apache/arrow/blob/8e43f23dcc6a9e630516228f110c48b64d13cec6/cpp/src/arrow/c/bridge.cc#L1332 >> Which seems to suggest it will always expect the validity bitmap. > > Not really. It expects one entry in the `buffers` array > (`n_buffers == 1`), but the entry can be NULL: > > """The pointer to the null bitmap buffer, if the data type specifies one, MAY > be NULL only if ArrowArray.null_count is 0.""" > > https://arrow.apache.org/docs/format/CDataInterface.html#c.ArrowArray.buffers > You can only see the corresponding logic in the import code here: > https://github.com/apache/arrow/blob/8e43f23dcc6a9e630516228f110c48b64d13cec6/cpp/src/arrow/c/bridge.cc#L1423-L1431 > > Regards > > Antoine.
