[GitHub] flink issue #3269: [FLINK-5698] Add NestedFieldsProjectableTableSource trait

[wuchong <gi...@git.apache.org>]

Github user wuchong commented on the issue:

    https://github.com/apache/flink/pull/3269
  
    Hi @tonycox , thanks for this PR. 
    
    It seems that you are using column names to represent the (nested) fields that are projected. I'm afraid that it can't work when the composite columns have the same nested field name. Such as a table schema `student<name, age>, teacher<name, age>`, and the projected fields are `name, age`, we can't determine whether the `name` is `student.name` or `teacher.name`.
    
    IMO, we can use the full qualifier column names with `.` separator to represent the (nested) fields. For the above example, the projected fields could be `student.name, teacher.age`. And then we can use it to do nested field projection push down.
    
    What do you think ? 
    
    Thanks,
    Jark Wu


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