[jira] [Created] (FLINK-12971) Remove the constraint that lookup join needs a primary key or index key

["Jark Wu (JIRA)" <ji...@apache.org>]

Jark Wu created FLINK-12971:
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             Summary: Remove the constraint that lookup join needs a primary key or index key
                 Key: FLINK-12971
                 URL: https://issues.apache.org/jira/browse/FLINK-12971
             Project: Flink
          Issue Type: Improvement
          Components: Table SQL / Planner
            Reporter: Jark Wu
            Assignee: Jark Wu


Currently, we add a constraint in dimension table lookup join that the lookup fields must be a primary key or index key. This is not a logic constraint but a performance constraint. Because if there are no indexes on the lookup key, the lookup performance will be poor. 

We will remove this constraint because not every table have a primary key or indexes (e.g. Hive tables). It's the user's responsibility if the lookup fields are not keys and get a bad performance. In this case, users should add indexes on these fields. In the future, we can also propagate out these tuning information before SQL is executed.



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