org.apache.flink.table.types.logical

Class LogicalType

java.lang.Object

org.apache.flink.table.types.logical.LogicalType

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

ArrayType, BigIntType, BinaryType, BooleanType, CharType, DateType, DayTimeIntervalType, DecimalType, DoubleType, FloatType, IntType, LegacyTypeInformationType, LocalZonedTimestampType, MapType, MultisetType, NullType, RawType, RowType, SmallIntType, SymbolType, TimestampType, TimeType, TinyIntType, TypeInformationRawType, UnresolvedUserDefinedType, UserDefinedType, VarBinaryType, VarCharType, YearMonthIntervalType, ZonedTimestampType

@PublicEvolving
public abstract class LogicalType
extends Object
implements Serializable

A logical type that describes the data type of a value. It does not imply a concrete physical representation for transmission or storage but defines the boundaries between JVM-based languages and the table ecosystem.

The definition of a logical type is similar to the SQL standard's "data type" terminology but also contains information about the nullability of a value for efficient handling of scalar expressions.

Subclasses of this class define characteristics of built-in or user-defined types. Every logical type must support nullability.

Instances of this class describe the fully parameterized, immutable type with additional information such as numeric precision or expected length.

Contracts how logical types relate to other types are defined by LogicalTypeCasts and LogicalTypeMerging.

NOTE: A logical type is just a description of a type, a planner or runtime might not support every type in every logical precision yet!

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LogicalType(boolean isNullable, LogicalTypeRoot typeRoot)

Method Summary

Modifier and Type	Method and Description
abstract <R> R	accept(LogicalTypeVisitor<R> visitor)
abstract String	asSerializableString() Returns a string that fully serializes this instance.
String	asSummaryString() Returns a string that summarizes this type for printing to a console.
protected static Set<String>	conversionSet(String... elements)
LogicalType	copy() Returns a deep copy of this type.
abstract LogicalType	copy(boolean isNullable) Returns a deep copy of this type with possibly different nullability.
boolean	equals(Object o)
abstract List<LogicalType>	getChildren()
abstract Class<?>	getDefaultConversion() Returns the default conversion class.
LogicalTypeRoot	getTypeRoot() Returns the root of this type.
int	hashCode()
boolean	is(LogicalTypeFamily family) Returns whether the family type of the type equals to the family or not.
boolean	is(LogicalTypeRoot typeRoot) Returns whether the root of the type equals to the typeRoot or not.
boolean	isAnyOf(LogicalTypeFamily... typeFamilies) Returns whether the root of the type is part of at least one family of the typeFamily or not.
boolean	isAnyOf(LogicalTypeRoot... typeRoots) Returns whether the root of the type equals to at least on of the typeRoots or not.
boolean	isNullable() Returns whether a value of this type can be null.
abstract 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.
abstract 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.
String	toString()
protected String	withNullability(String format, Object... params)

Methods inherited from class java.lang.Object

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

Constructor Detail

LogicalType

public LogicalType(boolean isNullable,
                   LogicalTypeRoot typeRoot)

Method Detail

isNullable

public boolean isNullable()

Returns whether a value of this type can be null.

getTypeRoot

public LogicalTypeRoot getTypeRoot()

Returns the root of this type. It is an essential description without additional parameters.

is

public boolean is(LogicalTypeRoot typeRoot)

Returns whether the root of the type equals to the typeRoot or not.

Parameters:

typeRoot - The root type to check against for equality

isAnyOf

public boolean isAnyOf(LogicalTypeRoot... typeRoots)

Returns whether the root of the type equals to at least on of the typeRoots or not.

Parameters:

typeRoots - The root types to check against for equality

isAnyOf

public boolean isAnyOf(LogicalTypeFamily... typeFamilies)

Returns whether the root of the type is part of at least one family of the typeFamily or not.

Parameters:

typeFamilies - The families to check against for equality

is

public boolean is(LogicalTypeFamily family)

Returns whether the family type of the type equals to the family or not.

Parameters:

family - The family type to check against for equality

copy

public abstract LogicalType copy(boolean isNullable)

Returns a deep copy of this type with possibly different nullability.

Parameters:

isNullable - the intended nullability of the copied type

Returns:

a deep copy

copy

public final LogicalType copy()

Returns a deep copy of this type. It requires an implementation of copy(boolean).

Returns:

a deep copy

asSerializableString

public abstract String asSerializableString()

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.

Returns:

detailed string for transmission or persistence

asSummaryString

public String asSummaryString()

Returns a string that summarizes this type for printing to a console. An implementation might shorten long names or skips very specific properties.

Use asSerializableString() for a type string that fully serializes this instance.

Returns:

summary string of this type for debugging purposes

supportsInputConversion

public abstract 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. 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.

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:

getDefaultConversion()

supportsOutputConversion

public abstract 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. 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.

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()

getDefaultConversion

public abstract Class<?> getDefaultConversion()

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.

Returns:

default class to represent values of this logical type

See Also:

supportsInputConversion(Class), supportsOutputConversion(Class)

getChildren

public abstract List<LogicalType> getChildren()

accept

public abstract <R> R accept(LogicalTypeVisitor<R> visitor)

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

withNullability

protected String withNullability(String format,
                                 Object... params)

conversionSet

protected static Set<String> conversionSet(String... elements)