Matt Topol created ARROW-2462: --------------------------------- Summary: [C++] Segfault when writing a parquet table containing a dictionary column from Record Batch Stream Key: ARROW-2462 URL: https://issues.apache.org/jira/browse/ARROW-2462 Project: Apache Arrow Issue Type: Bug Components: C++, Python Affects Versions: 0.9.1 Reporter: Matt Topol
Discovered this through using pyarrow and dealing with RecordBatch Streams and parquet. The issue can be replicated as follows: {code:python} import pyarrow as pa import pyarrow.parquet as pq # create record batch with 1 dictionary column indices = pa.array([1,0,1,1,0]) dictionary = pa.array(['Foo', 'Bar']) dict_array = pa.DictionaryArray.from_arrays(indices, dictionary) rb = pa.RecordBatch.from_arrays( [ dict_array ], [ 'd0' ] ) # write out using RecordBatchStreamWriter sink = pa.BufferOutputStream() writer = pa.RecordBatchStreamWriter(sink, rb.schema) writer.write_batch(rb) writer.close() buf = sink.get_result() # read in and try to write parquet table reader = pa.open_stream(buf) tbl = reader.read_all() pq.write_table(tbl, 'dict_table.parquet') # SEGFAULTS {code} When writing record batch streams, if there are no nulls in an array, Arrow will put a placeholder nullptr instead of putting the full bitmap of 1s, when deserializing that stream, the bitmap for the nulls isn't populated and is left to being a nullptr. When attempting to write this table via pyarrow.parquet, you end up [here|https://github.com/apache/parquet-cpp/blob/master/src/parquet/arrow/writer.cc#L963] in the parquet writer code which attempts to Cast the dictionary to a non-dictionary representation. Since the null count isn't checked before creating a BitmapReader, the BitmapReader is constructed with a nullptr for the bitmap_data, but a non-zero length which then segfaults in the constructor [here|https://github.com/apache/arrow/blob/master/cpp/src/arrow/util/bit-util.h#L415] because bitmap is null. So a simple check of the null count before constructing the BitmapReader avoids the segfault. Already filed [PR 1896|https://github.com/apache/arrow/pull/1896] -- This message was sent by Atlassian JIRA (v7.6.3#76005)