Package org.apache.flink.table.examples.java.functions

Class InternalRowMergerFunction

  • All Implemented Interfaces:
    Serializable, FunctionDefinition
    public final class InternalRowMergerFunction
extends ScalarFunction
    Merges two rows into a single row with unique field names.

    The function uses a custom TypeInference and thus disables any of the default reflection-based logic. It returns internal data structures for both input and output types of the eval method.

    For code readability, we might use some internal utility methods that should rarely change. Implementers can copy those if they don't want to rely on non-official API.

    See Also:
    Serialized Form

    • Constructor Detail

      • InternalRowMergerFunction

        public InternalRowMergerFunction()

    • Method Detail

      • getTypeInference

        public TypeInference getTypeInference​(DataTypeFactory typeFactory)
        Description copied from class: UserDefinedFunction
        Returns the logic for performing type inference of a call to this function definition.

        The type inference process is responsible for inferring unknown types of input arguments, validating input arguments, and producing result types. The type inference process happens independent of a function body. The output of the type inference is used to search for a corresponding runtime implementation.

        Instances of type inference can be created by using TypeInference.newBuilder().

        See BuiltInFunctionDefinitions for concrete usage examples.

        The type inference for user-defined functions is automatically extracted using reflection. It does this by analyzing implementation methods such as eval() or accumulate() and the generic parameters of a function class if present. If the reflective information is not sufficient, it can be supported and enriched with DataTypeHint and FunctionHint annotations.

        Note: Overriding this method is only recommended for advanced users. If a custom type inference is specified, it is the responsibility of the implementer to make sure that the output of the type inference process matches with the implementation method:

        The implementation method must comply with each DataType.getConversionClass() returned by the type inference. For example, if DataTypes.TIMESTAMP(3).bridgedTo(java.sql.Timestamp.class) is an expected argument type, the method must accept a call eval(java.sql.Timestamp).

        Regular Java calling semantics (including type widening and autoboxing) are applied when calling an implementation method which means that the signature can be eval(java.lang.Object).

        The runtime will take care of converting the data to the data format specified by the DataType.getConversionClass() coming from the type inference logic.

        Specified by:
        getTypeInference in interface FunctionDefinition
        Overrides:
        getTypeInference in class ScalarFunction