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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