Remi Dettai created ARROW-10577:
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Summary: [Rust][DataFusion] Hash Aggregator stream finishes
unexpectedly after going to Pending state
Key: ARROW-10577
URL: https://issues.apache.org/jira/browse/ARROW-10577
Project: Apache Arrow
Issue Type: Bug
Components: Rust, Rust - DataFusion
Affects Versions: 2.0.0
Reporter: Remi Dettai
This happens when executing a DataFusion query plan with hash aggregation where
the data source is not ready on the first call by the Executor, and the async
state machine is passed to a _pending_ state
In the {{Stream}} implem of {{GroupedHashAggregateStream}} and
{{HashAggregateStream}}, the state is set to {{self.finished = true}} on the
first call to {{poll_next()}}. If the inner stream is {{Poll::Pending}} on the
first call, this means that the next call resolves to {{Poll::Ready(None)}},
thus finishing the stream instead of actually consuming the inner data.
I think that it does not happen with most current sources because they never
trigger the {{Poll::Pending}} state. Parquet is implemented with a blocking
call inside {{poll_next()}} (which is also problematic but an other issue),
Memory yields directly, and CSV also always yields {{Poll::Ready}}
An analysis should be performed on all physical plans to check if the issue
occurs in other places.
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