Lijie Wang created FLINK-30601:
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Summary: Omit "setKeyContextElement" call for non-keyed
stream/operators to improve performance
Key: FLINK-30601
URL: https://issues.apache.org/jira/browse/FLINK-30601
Project: Flink
Issue Type: Improvement
Components: Runtime / Task
Reporter: Lijie Wang
Fix For: 1.17.0
Currently, flink will set the correct key context(by call
[setKeyContextElement|https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/ChainingOutput.java#:~:text=input.setKeyContextElement(castRecord)%3B])
before processing each record, which is typically used to extract key from
record and pass that key to the state backends.
However, the "setKeyContextElement" is obviously not need for non-keyed
stream/operator, in which case we should omit the "setKeyContextElement" calls
to improve performance. Note that setKeyContextElement is an interface method,
it requires looking up the interface table when calling, which will further
increase the method call overhead.
We run the following program as benchmark with parallelism=1 and object re-use
enabled. The benchmark results are averaged across 5 runs for each setup.
Before and after applying the proposed change, the average execution time
changed from 88.39 s to 78.76 s, which increases throughput by 10.8%.
{code:java}
env.fromSequence(1, 1000000000L)
.map(x -> x)
.map(x -> x)
.map(x -> x)
.map(x -> x)
.map(x -> x).addSink(new DiscardingSink<>());
{code}
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