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https://issues.apache.org/jira/browse/FLINK-3754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15260456#comment-15260456
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ASF GitHub Bot commented on FLINK-3754:
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Github user fhueske commented on the pull request:

    https://github.com/apache/flink/pull/1916#issuecomment-215142967
  
    Hi @yjshen, thanks for your patience. I also finished a first pass over the 
PR. 
    
    I'd like to propose a third alternative, in addition to the custom 
validation phase (this PR) and generating `SqlNode`s and using Calcite's 
validator. Both approaches would mean that the validation happens before the 
logical plan is translated into a `RelNode`. I think it would be good to 
eagerly check each method call of the Table API. This would make debugging 
easier, because exceptions would be thrown where the error is caused. Please 
correct me if I am wrong, but I think we would not lose validation coverage 
compared to the coverage this PR if we do eager validation? It might also be 
easier, because we do not need the recursive operator traversal (still the 
expression traversal though). Maybe we can even directly translate to 
`RelNode`s after validation, just like we do right now. I think a lot of this 
PR could be used for eager validation, not sure if it would be easily possible 
with the `SqlNode` validation approach. 
    What do you think about eagerly validation, @yjshen and @twalthr?
    
    While reviewing the PR, I noticed that some classes seem to be partially 
derived from Spark's code base (e.g., `TreeNode` and `RuleExecutor`). I know 
there are some common patterns that apply in optimizers, but it is good style 
to give credit to the original source code. 
    Can you list which classes are derived from Spark code and add a comment to 
them pointing to the source of the code?
    
    Thanks, Fabian


> Add a validation phase before construct RelNode using TableAPI
> --------------------------------------------------------------
>
>                 Key: FLINK-3754
>                 URL: https://issues.apache.org/jira/browse/FLINK-3754
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API
>    Affects Versions: 1.0.0
>            Reporter: Yijie Shen
>            Assignee: Yijie Shen
>
> Unlike sql string's execution, which have a separate validation phase before 
> RelNode construction, Table API lacks the counterparts and the validation is 
> scattered in many places.
> I suggest to add a single validation phase and detect problems as early as 
> possible.



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