Function duckdb_fetch_chunk 

pub unsafe extern "C" fn duckdb_fetch_chunk(
    result: duckdb_result,
) -> duckdb_data_chunk

Fetches a data chunk from a duckdb_result. This function should be called repeatedly until the result is exhausted.

The result must be destroyed with duckdb_destroy_data_chunk.

It is not known beforehand how many chunks will be returned by this result.

@param result The result object to fetch the data chunk from. @return The resulting data chunk. Returns NULL if the result has an error.