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

Class NullType

java.lang.Object
org.apache.flink.table.types.logical.LogicalType
org.apache.flink.table.types.logical.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:

  • Constructor Details

    • NullType

      public NullType()

  • Method Details

    • 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:

    • 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:

    • getDefaultConversion

      public Class<?> getDefaultConversion()
      Description copied from class: LogicalType
      Returns the default conversion class. A value of this logical type is expected to be an instance of the given class when entering or is represented as an instance of the given class when leaving the table ecosystem if no other conversion has been specified.

      For example, java.lang.Long is the default input and output for BIGINT.

      Specified by:
      getDefaultConversion in class LogicalType
      Returns:
      default class to represent values of this logical type
      See Also:

    • getChildren

      public List<LogicalType> getChildren()
      Specified by:
      getChildren in class LogicalType

    • accept

      public <R> R accept(LogicalTypeVisitor<R> visitor)
      Specified by:
      accept in class LogicalType