Package org.apache.flink.table.annotation

Annotation Type ProcedureHint

  • @PublicEvolving
@Retention(RUNTIME)
@Target({TYPE,METHOD})
@Repeatable(ProcedureHints.class)
public @interface ProcedureHint
    A hint that influences the reflection-based extraction of input types and output types for constructing the TypeInference logic of a Procedure.

    One or more annotations can be declared on top of a Procedure class or individually for each call() method for overloading function signatures. All hint parameters are optional. If a parameter is not defined, the default reflection-based extraction is used. Hint parameters defined on top of a Procedure class are inherited by all call() methods. The DataTypeHint for the output data type of a Procedure should always hint the component type of the array returned by Procedure.

    The following examples show how to explicitly specify procedure signatures as a whole or in part and let the default extraction do the rest: 

    {@code
 // accepts (INT, STRING) and returns BOOLEAN
    See Also:
    DataTypeHint

    • Optional Element Summary

      Optional Elements 
      Modifier and Type Optional Element Description
      ArgumentHint[] argument
      Explicitly lists the argument that a procedure takes as input, including their names, types, and whether they are optional.
      String[] argumentNames
      Explicitly lists the argument names that a procedure takes as input.
      DataTypeHint[] input
      Explicitly lists the argument types that a procedure takes as input.
      boolean isVarArgs
      Defines that the last argument type defined in input() should be treated as a variable-length argument.
      DataTypeHint output
      Explicitly defines the result type that a procedure uses as output.

    • Element Detail

      • input

        DataTypeHint[] input
        Explicitly lists the argument types that a procedure takes as input.

        By default, explicit input types are undefined and the reflection-based extraction is used.

        Note: Specifying the input arguments manually disables the entire reflection-based extraction around arguments. This means that also isVarArgs() and argumentNames() need to be specified manually if required.

        Default:
        {@org.apache.flink.table.annotation.DataTypeHint}

      • isVarArgs

        boolean isVarArgs
        Defines that the last argument type defined in input() should be treated as a variable-length argument.

        By default, if input() is defined, the last argument type is not a var-arg. If input() is not defined, the reflection-based extraction is used to decide about the var-arg flag, thus, this parameter is ignored.

        Default:
        false

      • argumentNames

        String[] argumentNames
        Explicitly lists the argument names that a procedure takes as input.

        By default, if input() is defined, explicit argument names are undefined and this parameter can be used to provide argument names. If input() is not defined, the reflection-based extraction is used, thus, this parameter is ignored.

        Default:
        {""}

      • argument

        ArgumentHint[] argument
        Explicitly lists the argument that a procedure takes as input, including their names, types, and whether they are optional.

        By default, it is recommended to use this parameter instead of input(). If the type of argumentHint is not defined, it will be considered an invalid argument and an exception will be thrown. Additionally, both this parameter and input() cannot be defined at the same time. If neither argument nor input() are defined, reflection-based extraction will be used.

        Default:
        {}

      • output

        DataTypeHint output
        Explicitly defines the result type that a procedure uses as output.

        By default, an explicit output type is undefined and the reflection-based extraction is used.

        Default:
        @org.apache.flink.table.annotation.DataTypeHint