QiuMM opened a new issue #6583: support rollup mode [COUNT() -> SUM(count)]
URL: https://github.com/apache/incubator-druid/issues/6583
 
 
   ### Motivation
   
   In my company, we use Druid as our OLAP engine that enables business users 
to analyze large quantities of data in real-time. However, druid will rollup 
data(if enable) at ingestion time. So when our users use `count()` in their 
sql, they often get unexpected results. Our users are not familiar with druid, 
it's hard for them to write a sql that will work as expected. So it would be 
better that druid support rollup mode, i.e. rewrite COUNT() to SUM(count), make 
it transparent to users.
   
   ### Proposed solution
   
   Add a boolean property `rollup` in `PlannerConfig` to indicate whether using 
the rollup mode or not. If it's true, in 
`CountSqlAggregator#toDruidAggregation` create a `LongSumAggregatorFactory` 
instead of a `CountAggregatorFactory`. 
   
   In `DruidSchema#analysisToRowSignature`, we can get aggregators info and 
find the defined count metric name, then using this name to construct a 
`LongSumAggregatorFactory`. However, currently I could not infer which one is 
the count aggregator from segment metadata query result, the related issue is 
#6578. 
   
   In order to support rollup mode, #6578 must be fixed first. Looking forward 
to your comments.

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