Suvayu Ali created ARROW-3792:
---------------------------------
Summary: [PARQUET] Segmentation fault when writing empty
RecordBatches
Key: ARROW-3792
URL: https://issues.apache.org/jira/browse/ARROW-3792
Project: Apache Arrow
Issue Type: Bug
Components: Format
Affects Versions: 0.11.1
Environment: Fedora 28, pyarrow installed with pip
Fedora 29, pyarrow installed from conda-forge
Reporter: Suvayu Ali
Attachments: pq-bug.py
h2. Background
I am trying to convert a very sparse dataset to parquet (~3% rows in a range
are populated). The file I am working with spans upto ~63M rows. I decided to
iterate in batches of 500k rows, 127 batches in total. Each row batch is a
RecordBatch. I create 4 batches at a time, and write to a parquet file
incrementally. Something like this:
{code:python}
batches = [..] # 4 batches
tbl = pa.Table.from_batches(batches)
pqwriter.write_table(tbl, row_group_size=15000)
# same issue with pq.write_table(..)
{code}
I was getting a segmentation fault at the final step, I narrowed it down to a
specific iteration. I noticed that iteration had empty batches; specifically,
[0, 0, 2876, 14423]. The number of rows for each RecordBatch for the whole
dataset is below:
{code:python}
[14050, 16398, 14080, 14920, 15527, 14288, 15040, 14733, 15345, 15799,
15728, 15942, 14734, 15241, 15721, 15255, 14167, 14009, 13753, 14800,
14554, 14287, 15393, 14766, 16600, 15675, 14072, 13263, 12906, 14167,
14455, 15428, 15129, 16141, 15478, 16257, 14639, 14887, 14919, 15535,
13973, 14334, 13286, 15038, 15951, 17252, 15883, 19903, 16967, 16878,
15845, 12205, 8761, 0, 0, 0, 0, 0, 2876, 14423, 13557, 12723, 14330,
15452, 13551, 12723, 12396, 13531, 13539, 11512, 13175, 13941, 14634,
15515, 14239, 13856, 13873, 14154, 14822, 13543, 14653, 15328, 16171,
15101, 150 55, 15194, 14058, 13706, 14747, 14650, 14694, 15397, 15122,
16055, 16635, 14153, 14665, 14781, 15462, 15426, 16150, 14632, 14532,
15139, 15324, 15279, 16075, 16394, 16834, 15391, 16320, 1650 4, 17248,
15913, 15341, 14754, 16637, 15695, 16642, 18143, 19481, 19072, 15742,
18807, 18789, 14258, 0, 0]
{code}
On excluding the empty RecordBatch-es, the segfault goes away, but
unfortunately I couldn't create a proper minimal example with synthetic data.
h2. Not quite minimal example
The data I am using is from the 1000 Genome project, which has been public for
many years, so we can be reasonably sure the data is good. The following steps
should help you replicate the issue.
# Download the data file (and index), about 330MB:
{code:bash}
$ wget
ftp://ftp.1000genomes.ebi.ac.uk/vol1/ftp/release/20130502/ALL.chr20.phase3_shapeit2_mvncall_integrated_v5a.20130502.genotypes.vcf.gz{,.tbi}
{code}
# Install the Cython library pysam, a thin wrapper around the reference
implementation of the VCF file spec. You will need zlib headers, but that's
probably not a problem :)
{code:bash}
$ pip3 install --user pysam
{code}
# Now you can use the attached script to replicate the crash.
h2. Extra information
I have tried attaching gdb, the backtrace when the segfault occurs is shown
below (maybe it helps, this is how I realised empty batches could be the
reason).
{code}
(gdb) bt
#0 0x00007f3e7676d670 in
parquet::TypedColumnWriter<parquet::DataType<(parquet::Type::type)6>
>::WriteMiniBatch(long, short const*, short const*, parquet::ByteArray const*)
()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/../../../libparquet.so.11
#1 0x00007f3e76733d1e in arrow::Status parquet::arrow::(anonymous
namespace)::ArrowColumnWriter::TypedWriteBatch<parquet::DataType<(parquet::Type::type)6>,
arrow::BinaryType>(arrow::Array const&, long, short const*, short const*) ()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/../../../libparquet.so.11
#2 0x00007f3e7673a3d4 in parquet::arrow::(anonymous
namespace)::ArrowColumnWriter::Write(arrow::Array const&) ()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/../../../libparquet.so.11
#3 0x00007f3e7673df09 in
parquet::arrow::FileWriter::Impl::WriteColumnChunk(std::shared_ptr<arrow::ChunkedArray>
const&, long, long) ()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/../../../libparquet.so.11
#4 0x00007f3e7673c74d in
parquet::arrow::FileWriter::WriteColumnChunk(std::shared_ptr<arrow::ChunkedArray>
const&, long, long) ()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/../../../libparquet.so.11
#5 0x00007f3e7673c8d2 in parquet::arrow::FileWriter::WriteTable(arrow::Table
const&, long) ()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/../../../libparquet.so.11
#6 0x00007f3e731e3a51 in
__pyx_pw_7pyarrow_8_parquet_13ParquetWriter_5write_table(_object*, _object*,
_object*) ()
from
/home/user/miniconda3/lib/python3.6/site-packages/pyarrow/_parquet.cpython-36m-x86_64-linux-gnu.so
{code}
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