A. Coady created ARROW-15318:
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Summary: [C++][Python] Regression reading partition keys of large
batches.
Key: ARROW-15318
URL: https://issues.apache.org/jira/browse/ARROW-15318
Project: Apache Arrow
Issue Type: Bug
Components: C++, Python
Affects Versions: 7.0.0
Reporter: A. Coady
In a partitioned dataset with chunks larger than the default 1Gi batch size,
reading _only_ the partition keys is hanging, and consuming unbounded memory.
The bug first appeared in nightly build `7.0.0.dev468`.
{code:python}
In [1]: import pyarrow as pa, pyarrow.parquet as pq, numpy as np
In [2]: pa.__version__
Out[2]: '7.0.0.dev468'
In [3]: table = pa.table({'key': pa.repeat(0, 2 ** 20 + 1), 'value':
np.arange(2 ** 20 + 1)})
In [4]: pq.write_to_dataset(table[:2 ** 20], 'one', partition_cols=['key'])
In [5]: pq.write_to_dataset(table[:2 ** 20 + 1], 'two', partition_cols=['key'])
In [6]: pq.read_table('one', columns=['key'])['key'].num_chunks
Out[6]: 1
In [7]: pq.read_table('two', columns=['key', 'value'])['key'].num_chunks
Out[7]: 2
In [8]: pq.read_table('two', columns=['key'])['key'].num_chunks
zsh: killed ipython # hangs; kllled
{code}
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