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https://issues.apache.org/jira/browse/FLINK-3754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15280178#comment-15280178
 ] 

ASF GitHub Bot commented on FLINK-3754:
---------------------------------------

Github user yjshen commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1958#discussion_r62855247
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/expressions/call.scala
 ---
    @@ -18,85 +18,26 @@
     package org.apache.flink.api.table.expressions
     
     import org.apache.calcite.rex.RexNode
    -import org.apache.calcite.sql.SqlOperator
    -import org.apache.calcite.sql.fun.SqlStdOperatorTable
     import org.apache.calcite.tools.RelBuilder
    +import org.apache.flink.api.table.validate.{ExprValidationResult, 
ValidationFailure}
     
     /**
       * General expression for unresolved function calls. The function can be 
a built-in
       * scalar function or a user-defined scalar function.
       */
    -case class Call(functionName: String, args: Expression*) extends 
Expression {
    +case class Call(functionName: String, args: Seq[Expression]) extends 
Expression {
    --- End diff --
    
    While I was resolving `Call` into solid expressions, `FunctionCatalog` is 
used and its `withChildren`  method is looking up constructors to create new 
`expression` as follows: 
    
    1. look up expressions take `Seq[Expression]` as argument
    2. if 1 is not fulfilled, look up the constructor match exactly the number 
of arguments, like the `MyFunc` example you provided.
    
    Does this make sense?


> 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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