[GitHub] [incubator-doris] ccoffline opened a new issue #5212: [Feature] SessionVariable broadcast_mem_limit

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

ccoffline opened a new issue #5212:
URL: https://github.com/apache/incubator-doris/issues/5212


   **Is your feature request related to a problem? Please describe.**
   
   One of the join strategies for now is to predict whether the broadcast join will exceed the memory limit. 
   https://github.com/apache/incubator-doris/blob/65d33cf43c837e56a2a36e78b358bfc0a9d1916b/fe/fe-core/src/main/java/org/apache/doris/planner/DistributedPlanner.java#L356-L378
   
   The variable `HASH_TBL_SPACE_OVERHEAD = 1.1` is inappropriate, which causes many large JOIN queries to use broadcast join.
   https://github.com/apache/incubator-doris/blob/65d33cf43c837e56a2a36e78b358bfc0a9d1916b/fe/fe-core/src/main/java/org/apache/doris/planner/PlannerContext.java#L37-L39
   
   **Describe the solution you'd like**
   
   Add a new variable `broadcast_mem_limit` and set `1G` as defaults.
   
   


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