org.apache.flink.table.types.logical.utils

Class LogicalTypeCasts

java.lang.Object

org.apache.flink.table.types.logical.utils.LogicalTypeCasts

@Internal
public final class LogicalTypeCasts
extends Object

Utilities for casting LogicalType.

This class aims to be compatible with the SQL standard. It is inspired by Apache Calcite's SqlTypeUtil#canCastFrom method.

Casts can be performed in two ways: implicit or explicit.

Explicit casts correspond to the SQL cast specification and represent the logic behind a CAST(sourceType AS targetType) operation. For example, it allows for converting most types of the LogicalTypeFamily.PREDEFINED family to types of the LogicalTypeFamily.CHARACTER_STRING family.

Implicit casts are used for safe type widening and type generalization (finding a common supertype for a set of types) without loss of information. Implicit casts are similar to the Java semantics (e.g. this is not possible: int x = (String) z).

Conversions that are defined by the LogicalType (e.g. interpreting a DateType as integer value) are not considered here. They are an internal bridging feature that is not standard compliant. If at all, CONVERT methods should make such conversions available.

Method Summary

Modifier and Type	Method and Description
static boolean	supportsExplicitCast(LogicalType sourceType, LogicalType targetType) Returns whether the source type can be casted to the target type.
static boolean	supportsImplicitCast(LogicalType sourceType, LogicalType targetType) Returns whether the source type can be safely casted to the target type without loosing information.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

supportsImplicitCast

public static boolean supportsImplicitCast(LogicalType sourceType,
                                           LogicalType targetType)

Returns whether the source type can be safely casted to the target type without loosing information.

Implicit casts are used for type widening and type generalization (finding a common supertype for a set of types). Implicit casts are similar to the Java semantics (e.g. this is not possible: int x = (String) z).

supportsExplicitCast

public static boolean supportsExplicitCast(LogicalType sourceType,
                                           LogicalType targetType)

Returns whether the source type can be casted to the target type.

Explicit casts correspond to the SQL cast specification and represent the logic behind a CAST(sourceType AS targetType) operation. For example, it allows for converting most types of the LogicalTypeFamily.PREDEFINED family to types of the LogicalTypeFamily.CHARACTER_STRING family.