Wenzhe Zhou created IMPALA-12909:
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             Summary: Generate distributed plan for query accessing multiple 
JDBC tables
                 Key: IMPALA-12909
                 URL: https://issues.apache.org/jira/browse/IMPALA-12909
             Project: IMPALA
          Issue Type: Sub-task
          Components: Frontend
            Reporter: Wenzhe Zhou


For a query which access multiple JDBC tables, Planner generate single node 
plan. It's better to generate distributed plan so that Impala could open 
multiple JDBC connections in parallel. This restriction is due to current 
design of External data source framework because scan is single threaded. 
DataSourceScanNode cannot run in node other than coordinator. 
There is no issue for query with join between JDBC table and non JDBC table. We 
have this issue only for all scans as JDBC table scans.



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