Jinfeng Ni created DRILL-2269:
---------------------------------

             Summary: Provide default implementation for getting cost of 
evaluating an expression in base class of LogicalExpression, in stead of throw 
Exception 
                 Key: DRILL-2269
                 URL: https://issues.apache.org/jira/browse/DRILL-2269
             Project: Apache Drill
          Issue Type: Bug
            Reporter: Jinfeng Ni


Today, the abstract class of LogicalExpression will throw Exception for two 
methods related to estimate the cost of evaluating an expression, in the hope 
that sub classes will override those two methods. However, if someone forgets 
to override, compiler and mvn build process will still be successful, yet will 
hit Exception in execution-time, complaining the sub class does not implement 
these methods.  As Drill's adding more sub classes of LogicalExpression to the 
code base, it's more likely for someone to forget to override those two 
methods, making it error-prone to just throw Exception in the base class.

In stead, we should provide a default implementation for those two methods in 
the base class. Certain sub classes will override to change the behavior. 
  

 



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