[GitHub] flink pull request: [FLINK-1297] Added OperatorStatsAccumulator fo...

[tammymendt <gi...@git.apache.org>]

Github user tammymendt commented on the pull request:

    https://github.com/apache/flink/pull/605#issuecomment-127519735
  
    Hey! So I've been using and testing this code throughout my master thesis. Collecting count distinct makes jobs about 10% slower whereas collecting heavy hitters can make a job be 20 to 50% slower (depending on the algorithm and the distribution of the data). However this overhead is lower than that of using a histogram accumulator (not to mention the histogram might not fit in memory). I think it can be a nice addition to the code, specially since it does not affect any core components. 
    
    The version that I pushed now uses a bunch of conditionals to check which statistic is being collected. I know @fhueske did not really like this. I implemented another version which avoids the conditionals by using a different class for every type of statistic. I preferred to push this version though, since it has been more thoroughly tested.


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