[GitHub] QiuMM opened a new issue #6583: support rollup mode [COUNT() -> SUM(count)]

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

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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