[GitHub] yurmix commented on issue #6320: Moving Average query type

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yurmix commented on issue #6320: Moving Average query type
URL: https://github.com/apache/incubator-druid/issues/6320#issuecomment-463471858
 
 
   @jihoonson The similarity between `PostAggregator` and `Averager` is that they both run post the query aggregation. They run in the Broker on the aggregated resultset. But while `PostAggregator` works on a single `Row` in the post-aggregation result set, `Averager` aggregated data over multiple Rows.
   
   How? Averagers collects previous records into a buffer (called `BaseAverager.buckets`) and uses that to compute a moving-average result for each Row. In the code, there is a collaberation between `Averager` and `MovingAverageIterable` to iterate over GroupBy's result-set while keeping a buffer and while returning the averager's result per each record.
   
   You can take a look at MovingAverageIterable and how `MovingAverageIterable#computeMovingAverage()` is calling `Averager#getResult()` -> `BaseAverager#computeResults()`.
   https://github.com/apache/incubator-druid/pull/6430/files#diff-0cbedd32f92fe9f41d7c47a628a2974fR270

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