[GitHub] [druid] jobar opened a new issue #11264: SQL query uses TopN when grouping by time and other dimension

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

jobar opened a new issue #11264:
URL: https://github.com/apache/druid/issues/11264


   ### Description
   
   When querying the SQL druid endpoint with a query doing a group-by on two fields and on of them is time related, the TopN query-type could be used instead of the group-by one, with the time grouping being implemented as "granularity".
   
   Example:
   ```
   EXPLAIN PLAN FOR
   SELECT FLOOR("__time" TO MONTH) AS "__timestamp",
          "my_field" AS "my_field",
          SUM(my_value) AS "sum_my_value"
   FROM my_data_source
   WHERE "__time" >= '...'
     AND "__time" < '...'
   GROUP BY "my_field", "FLOOR("__time" TO MONTH)
   ORDER BY sum_my_value
   LIMIT 500;
   
   DruidQueryRel(query=[{"queryType":"groupBy","dataSource":{"type":"table","name":"my_data_source"}...
   ```
   
   ### Motivation
   
   Group-by queries are a lot more expensive than TopN queries, this change would allow to get results a lot faster and cheaper.
   


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