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.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
NullType()

Method Summary

Modifier and Type	Method and Description
<R> R	accept(LogicalTypeVisitor<R> visitor)
String	asSerializableString() Returns a string that fully serializes this instance.
LogicalType	copy(boolean isNullable) Returns a deep copy of this type with possibly different nullability.
List<LogicalType>	getChildren()
Class<?>	getDefaultConversion() Returns the default conversion class.
boolean	supportsInputConversion(Class<?> clazz) Returns whether an instance of the given class can be represented as a value of this logical type when entering the table ecosystem.
boolean	supportsOutputConversion(Class<?> clazz) Returns whether a value of this logical type can be represented as an instance of the given class when leaving the table ecosystem.

Methods inherited from class org.apache.flink.table.types.logical.LogicalType

asSummaryString, conversionSet, copy, equals, getTypeRoot, hashCode, isNullable, toString, withNullability

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

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()

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:

LogicalType.supportsInputConversion(Class), LogicalType.supportsOutputConversion(Class)

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