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From aljoscha <...@git.apache.org>
Subject [GitHub] flink pull request #2277: [FLINK-4207] WindowOperator becomes very slow with...
Date Mon, 25 Jul 2016 13:55:58 GMT
Github user aljoscha commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2277#discussion_r72067210
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/windowing/WindowOperator.java
---
    @@ -408,11 +410,22 @@ public void processWatermark(Watermark mark) throws Exception {
     				if (windowAssigner instanceof MergingWindowAssigner) {
     					mergingWindows = getMergingWindowSet();
     					W stateWindow = mergingWindows.getStateWindow(context.window);
    +					if (stateWindow == null) {
    +						// then the window is already purged and this is a cleanup
    +						// timer set due to allowed lateness that has nothing to clean,
    +						// so it is safe to just ignore
    +						continue;
    +					}
     					windowState = getPartitionedState(stateWindow, windowSerializer, windowStateDescriptor);
     				} else {
     					windowState = getPartitionedState(context.window, windowSerializer, windowStateDescriptor);
     				}
     
    +				if (windowState.get() == null) {
    --- End diff --
    
    This doubles the amount of accesses to the state. For example, for RocksDB that's two
DB lookups instead of one. I think we can get the state contents once and pass that to `fireOrContinue()`
instead of the state object. 
    
    Same for other instances of this snipped. 


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