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https://issues.apache.org/jira/browse/ARROW-13982?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Li resolved ARROW-13982.
------------------------------
Resolution: Fixed
Issue resolved by pull request 11145
[https://github.com/apache/arrow/pull/11145]
> [C++] Async scanner stalls if a fragment generates no batches
> -------------------------------------------------------------
>
> Key: ARROW-13982
> URL: https://issues.apache.org/jira/browse/ARROW-13982
> Project: Apache Arrow
> Issue Type: Bug
> Components: C++
> Affects Versions: 5.0.0
> Environment: ubuntu 18.04 LTS
> Reporter: Huxley Hu
> Assignee: David Li
> Priority: Critical
> Labels: pull-request-available, query-engine
> Fix For: 6.0.0
>
> Attachments: repro.py
>
> Time Spent: 2h 40m
> Remaining Estimate: 0h
>
> Reading parquet files using dataset scanner may stall due to a never-finished
> future.
> To reproduce this case, one needs two parquet files and sets the filter
> expression to something that could filter one file completely. After that,
> calling `AsyncScanner::ToRecordBatchReader` and read data continually.
> I also have dug this bug a little. It's caused by the
> `MakeEmptyGenerator<std::shared_ptr<RecordBatch>>` when filtered row groups
> is empty, which's ignored by `FragmentToBatches` and causes
> SequencingGenerator to stall.
> A quick fix is to return a record batch with 0 rows instead of returning a
> nullptr there.
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