Package org.apache.flink.table.types.logical

Class NullType

  • All Implemented Interfaces:
    Serializable
    @PublicEvolving
public final class NullType
extends LogicalType
    Logical type for representing untyped NULL values. The null type is an extension to the SQL standard. A null type has no other value except NULL, thus, it can be cast to any nullable type similar to JVM semantics.

    This type helps in representing unknown types in API calls that use a NULL literal as well as bridging to formats such as JSON or Avro that define such a type as well.

    The serialized string representation is NULL.

    Note: The runtime does not support this type. It is a pure helper type during translation and planning. Table columns cannot be declared with this type. Functions cannot declare return types of this type.

    See Also:
    Serialized Form

    • Constructor Detail

      • NullType

        public NullType()

    • Method Detail

      • copy

        public LogicalType copy​(boolean isNullable)
        Description copied from class: LogicalType
        Returns a deep copy of this type with possibly different nullability.
        Specified by:
        copy in class LogicalType
        Parameters:
        isNullable - the intended nullability of the copied type
        Returns:
        a deep copy

      • asSerializableString

        public String asSerializableString()
        Description copied from class: LogicalType
        Returns a string that fully serializes this instance. The serialized string can be used for transmitting or persisting a type.

        See LogicalTypeParser for the reverse operation.

        Specified by:
        asSerializableString in class LogicalType
        Returns:
        detailed string for transmission or persistence

      • supportsInputConversion

        public boolean supportsInputConversion​(Class<?> clazz)
        Description copied from class: LogicalType
        Returns whether an instance of the given class can be represented as a value of this logical type when entering the table ecosystem. This method helps for the interoperability between JVM-based languages and the relational type system.

        A supported conversion directly maps an input class to a logical type without loss of precision or type widening.

        For example, java.lang.Long or long can be used as input for BIGINT independent of the set nullability.

        Specified by:
        supportsInputConversion in class LogicalType
        Parameters:
        clazz - input class to be converted into this logical type
        Returns:
        flag that indicates if instances of this class can be used as input into the table ecosystem
        See Also:
        LogicalType.getDefaultConversion()

      • supportsOutputConversion

        public boolean supportsOutputConversion​(Class<?> clazz)
        Description copied from class: LogicalType
        Returns whether a value of this logical type can be represented as an instance of the given class when leaving the table ecosystem. This method helps for the interoperability between JVM-based languages and the relational type system.

        A supported conversion directly maps a logical type to an output class without loss of precision or type widening.

        For example, java.lang.Long or long can be used as output for BIGINT if the type is not nullable. If the type is nullable, only java.lang.Long can represent this.

        Specified by:
        supportsOutputConversion in class LogicalType
        Parameters:
        clazz - output class to be converted from this logical type
        Returns:
        flag that indicates if instances of this class can be used as output from the table ecosystem
        See Also:
        LogicalType.getDefaultConversion()