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• If a OneInputTransformation has isInternalSorterSupported == false, keyed input, and execution.checkpointing.interval-during-backlog == 0:
  • Flink runtime will add an external sorter for the input to sort the keyed input during backlog processing
  • Its managed memory should be set according to execution.sorted-inputs.memory

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• • Use a state backend with cache introduced in FLIP-325

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• • with a cache size of 1 if the cache size isn't explicitly specified by users so that we optimize the state backend access while minimizing the memory overhead. Alternatively, when users have set a cache size, we will adhere to that setting.

With the above change, we This optimization can significantly enhance the performance of keyed one input operators without code change when "isBacklog=true". Moreover, the performance of the operator during isBacklog=true is close to the performance in batch mode.

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