[GitHub] fhueske commented on issue #6987: [FLINK-8897] [table] Fix rowtime materialization issues for filters and joins

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fhueske commented on issue #6987: [FLINK-8897] [table] Fix rowtime materialization issues for filters and joins
URL: https://github.com/apache/flink/pull/6987#issuecomment-435869177
 
 
   Hi @hequn8128, the problem with throwing exceptions in the rules is that they result in canceling the optimizer completely, i.e., as soon as a rule is applied on a plan that does not meet the condition, the query fails even if the query could be transformed into a valid execution plan. I know that Calcite's "Cannot optimize" exceptions are hard to digest, but they are only thrown when the optimizer cannot generate a valid plan. 
   
   Aborting the optimization is especially tricky for specialized operators like window join that require very specific conditions. If these conditions are not met, the join can often be executed with a regular (fully materializing) join. I don't think we should speculate whether this is something that the user intended to do or not.
   

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