Package org.apache.calcite.util.mapping

Enum MappingType

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Comparable<MappingType>
    public enum MappingType
extends java.lang.Enum<MappingType>
    Describes the type of a mapping, from the most general MULTI_FUNCTION (every element in the source and target domain can participate in many mappings) to the most retricted BIJECTION (every element in the source and target domain must be paired with precisely one element in the other domain).

    Some common types:

    • A surjection is a mapping if every target has at least one source; also known as an 'onto' mapping.
    • A mapping is a partial function if every source has at most one target.
    • A mapping is a function if every source has precisely one target.
    • An injection is a mapping where a target has at most one source; also somewhat confusingly known as a 'one-to-one' mapping.
    • A bijection is a mapping which is both an injection and a surjection. Every source has precisely one target, and vice versa.

    Once you know what type of mapping you want, call Mappings.create(MappingType, int, int) to create an efficient implementation of that mapping.

    • Enum Constant Detail

      • SURJECTION

        public static final MappingType SURJECTION

      • INVERSE_SURJECTION

        public static final MappingType INVERSE_SURJECTION
        An inverse surjection has a source for every target, and no source has more than one target.

      • PARTIAL_SURJECTION

        public static final MappingType PARTIAL_SURJECTION
        A partial surjection has no more than one source for any target, and no more than one target for any source.

      • PARTIAL_INJECTION

        public static final MappingType PARTIAL_INJECTION

      • PARTIAL_FUNCTION

        public static final MappingType PARTIAL_FUNCTION

      • INVERSE_INJECTION

        public static final MappingType INVERSE_INJECTION

      • INVERSE_PARTIAL_INJECTION

        public static final MappingType INVERSE_PARTIAL_INJECTION

      • INVERSE_PARTIAL_FUNCTION

        public static final MappingType INVERSE_PARTIAL_FUNCTION

      • MULTI_FUNCTION

        public static final MappingType MULTI_FUNCTION

    • Field Detail

      • inverseOrdinal

        private final int inverseOrdinal

      • OPTIONAL_SOURCE

        private static final int OPTIONAL_SOURCE
        Allow less than one source for a given target.
        See Also:
        Constant Field Values

      • MULTIPLE_SOURCE

        private static final int MULTIPLE_SOURCE
        Allow more than one source for a given target.
        See Also:
        Constant Field Values

      • OPTIONAL_TARGET

        private static final int OPTIONAL_TARGET
        Allow less than one target for a given source.
        See Also:
        Constant Field Values

      • MULTIPLE_TARGET

        private static final int MULTIPLE_TARGET
        Allow more than one target for a given source.
        See Also:
        Constant Field Values

    • Constructor Detail

      • MappingType

        private MappingType()

    • Method Detail

      • values

        public static MappingType[] values()
        Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows: 
        for (MappingType c : MappingType.values())
    System.out.println(c);
        Returns:
        an array containing the constants of this enum type, in the order they are declared

      • valueOf

        public static MappingType valueOf​(java.lang.String name)
        Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
        Parameters:
        name - the name of the enum constant to be returned.
        Returns:
        the enum constant with the specified name
        Throws:
        java.lang.IllegalArgumentException - if this enum type has no constant with the specified name
        java.lang.NullPointerException - if the argument is null

      • isA

        public boolean isA​(MappingType mappingType)
        Returns whether this mapping type is (possibly a weaker form of) a given mapping type.

        For example, a BIJECTION is a FUNCTION, but not every {link #Function} is a BIJECTION.

      • isFunction

        public boolean isFunction()
        A mapping is a total function if every source has precisely one target.

      • isPartialFunction

        public boolean isPartialFunction()
        A mapping is a partial function if every source has at most one target.

      • isSurjection

        public boolean isSurjection()
        A mapping is a surjection if it is a function and every target has at least one source.

      • isInjection

        public boolean isInjection()
        A mapping is an injection if it is a function and no target has more than one source. (In other words, every source has precisely one target.)

      • isBijection

        public boolean isBijection()
        A mapping is a bijection if it is a surjection and it is an injection. (In other words,

      • isMandatoryTarget

        public boolean isMandatoryTarget()
        Constraint that every source has at least one target.

      • isSingleTarget

        public boolean isSingleTarget()
        Constraint that every source has at most one target.

      • isMandatorySource

        public boolean isMandatorySource()
        Constraint that every target has at least one source.

      • isSingleSource

        public boolean isSingleSource()
        Constraint that every target has at most one source.