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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3450: [FLINK-5794][doc] update the documentation about ...
Date Wed, 01 Mar 2017 17:57:40 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3450#discussion_r103746007
  
    --- Diff: docs/dev/table_api.md ---
    @@ -4732,23 +4732,29 @@ User-defined Functions
     
     If a required scalar function is not contained in the built-in functions, it is possible
to define custom, user-defined scalar functions for both the Table API and SQL. A user-defined
scalar functions maps zero, one, or multiple scalar values to a new scalar value.
     
    -In order to define a scalar function one has to extend the base class `ScalarFunction`
in `org.apache.flink.table.functions` and implement (one or more) evaluation methods. The
behavior of a scalar function is determined by the evaluation method. An evaluation method
must be declared publicly and named `eval`. The parameter types and return type of the evaluation
method also determine the parameter and return types of the scalar function. Evaluation methods
can also be overloaded by implementing multiple methods named `eval`.
    +In order to define a scalar function one has to extend the base class `ScalarFunction`
in `org.apache.flink.table.functions` and implement (one or more) evaluation methods. Moreover
constructor of the user-defined scalar function can contain constructor arguments. The behavior
of a scalar function is determined by the evaluation method. An evaluation method must be
declared publicly and named `eval`. The parameter types and return type of the evaluation
method also determine the parameter and return types of the scalar function. Evaluation methods
can also be overloaded by implementing multiple methods named `eval`.
    --- End diff --
    
    I would remove the sentence about the constructor because it breaks the explanation flow.



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