Jayjeet Chakraborty created ARROW-13088:
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Summary: Dataset API calls with nested parallelism does not
progress
Key: ARROW-13088
URL: https://issues.apache.org/jira/browse/ARROW-13088
Project: Apache Arrow
Issue Type: Bug
Components: C++
Affects Versions: 4.0.1, 3.0.0
Reporter: Jayjeet Chakraborty
Launching nested threads using the C++ ThreadPool causes the Dataset API
(C++/Python using the SyncScanner/AsyncScanner) to stop progressing. The
execution just hangs and keeps waiting. Examples of nested threading:
# Force turn on parallel column reads in ParquetFileFormat by tweaking the
code
[here|https://github.com/apache/arrow/blob/master/cpp/src/arrow/dataset/file_parquet.cc#L327]
to get into nested parallelism (for every scan task launched in parallel to
spawn threads internally).
# Create a simple dataset containing Parquet files of count X (where X >= No.
of logical cores).
# {{Just to a dataset.to_table() call.}}
The execution should stop and go into a kind of a sleep state immediately.
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