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

Class MultisetType

  • All Implemented Interfaces:
    Serializable
    @PublicEvolving
public final class MultisetType
extends LogicalType
    Logical type of a multiset (=bag). Unlike a set, it allows for multiple instances for each of its elements with a common subtype. Each unique value (including NULL) is mapped to some multiplicity. There is no restriction of element types; it is the responsibility of the user to ensure uniqueness.

    The serialized string representation is MULTISET<t> where t is the logical type of the contained elements. t MULTISET is a synonym for being closer to the SQL standard.

    A conversion is possible through a map that assigns each value to an integer multiplicity (Map<t, Integer>).

    See Also:
    Serialized Form

    • Constructor Detail

      • MultisetType

        public MultisetType​(boolean isNullable,
                    LogicalType elementType)

      • MultisetType

        public MultisetType​(LogicalType elementType)

    • 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

      • asSummaryString

        public String asSummaryString()
        Description copied from class: LogicalType
        Returns a string that summarizes this type for printing to a console. An implementation might shorten long names or skips very specific properties.

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

        Overrides:
        asSummaryString in class LogicalType
        Returns:
        summary string of this type for debugging purposes

      • 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()