[GitHub] [incubator-druid] himanshug opened a new pull request #8412: skip unnecessary aggregate(..) calls with LimitedBufferHashGrouper

[GitBox <gi...@apache.org>]

himanshug opened a new pull request #8412: skip unnecessary aggregate(..) calls with LimitedBufferHashGrouper
URL: https://github.com/apache/incubator-druid/pull/8412
 
 
   ### Description
   
   This is a short patch removing unnecessary work done during execution of groupBy query with limit push down. When limit is pushed down to merge phase in the groupBy query processing , `aggregate(..)` is called for all aggregators whenever a new bucket is added to the underlying hash table. This is unnecessary when `sortHasNonGroupingFields=false` and newly added bucket did not find a place in the min-max-heap .  With `sortHasNonGroupingFields=false`, that row's position in overall ordering can never change so it is ok to skip the `aggregate(..)` calls. this improves performance for cases where you have large number of buckets with multiple complex aggregators.
   
   No behavior change is introduced in this PR.
   
   <hr>
   
   This PR has:
   - [X] been self-reviewed.
   - [X] been tested in a test Druid cluster.
   <hr>
   

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