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ASF GitHub Bot updated ARROW-2462: ---------------------------------- Labels: pull-request-available (was: ) > [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 > Priority: Major > Labels: pull-request-available > > 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)