Fu Kai created FLINK-22113:
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             Summary: UniqueKey constraint is lost with multiple sources join 
in SQL
                 Key: FLINK-22113
                 URL: https://issues.apache.org/jira/browse/FLINK-22113
             Project: Flink
          Issue Type: Bug
          Components: Table SQL / Planner
    Affects Versions: 1.13.0
            Reporter: Fu Kai


Hi team,
 
We have a use case to join multiple data sources to generate a continuous 
updated view. We defined primary key constraint on all the input sources and 
all the keys are the subsets in the join condition. All joins are left join.
 
In our case, the first two inputs can produce *JoinKeyContainsUniqueKey* input 
sepc, which is good and performant. While when it comes to the third input 
source, it's joined with the intermediate output table of the first two input 
tables, and the intermediate table does not carry key constraint 
information(although the thrid source input table does), so it results in a 
*NoUniqueKey* input sepc. Given NoUniqueKey inputs has dramatic performance 
implications per the[ Force Join Unique 
Key|http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Force-Join-Unique-Key-td39521.html#a39651]
 email thread, we want to know if there is any mitigation solution for this.
 



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