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https://issues.apache.org/jira/browse/FLINK-30533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dong Lin reassigned FLINK-30533:
--------------------------------
Assignee: Dong Lin
> IteratorSourceReaderBase#pollNext() should push records to ReaderOutput in a
> while loop
> ---------------------------------------------------------------------------------------
>
> Key: FLINK-30533
> URL: https://issues.apache.org/jira/browse/FLINK-30533
> Project: Flink
> Issue Type: Sub-task
> Reporter: Dong Lin
> Assignee: Dong Lin
> Priority: Major
>
> Currently, each invocation of IteratorSourceReaderBase#pollNext() push at
> most one record to the given ReaderOutput. This unnecessarily increases the
> average Java call stack depth needed to produce an element.
>
> Take the following program as an example. For each element produced by this
> program, Flink runtime needs to include in the call stack these 4 function
> calls:
> * StreamTask#processInput()
> * StreamOneInputProcessor#processInput()
> * StreamTaskSourceInput#emitNext()
> * SourceOperator#emitNext()
> {code:java}
> DataStream<Long> stream = env.fromSequence(1, 1000000000L)
> .map(x -> x)
> .addSink(new DiscardingSink<>());
> {code}
>
> In comparison, SourceReaderBase#pollNext() is already using a while loop so
> that each invocation of this method could push as many records to the given
> ReaderOutput as possible.
>
> This ticket proposes to update IteratorSourceReaderBase#pollNext() to push
> records to ReaderOutput in a while loop, for the following two reason:
> * It improves performance for programs that IteratorSourceReaderBase (e.g.
> env.fromSequence) by removing an average of 4 function from the call stack
> needed to produce a record.
> * It makes the behavior of IteratorSourceReaderBase and SourceReaderBase
> consistent with each other.
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