Package org.apache.calcite.util.mapping

Enum MappingType

java.lang.Object
java.lang.Enum<MappingType>
org.apache.calcite.util.mapping.MappingType
All Implemented Interfaces:
Serializable, Comparable<MappingType>, Constable
public enum MappingType extends 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 restricted 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 Details

    • BIJECTION

      public static final MappingType BIJECTION

    • SURJECTION

      public static final MappingType SURJECTION

    • INJECTION

      public static final MappingType INJECTION

    • FUNCTION

      public static final MappingType FUNCTION

    • 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

    • TEN

      public static final MappingType TEN

    • ELEVEN

      public static final MappingType ELEVEN

    • INVERSE_FUNCTION

      public static final MappingType INVERSE_FUNCTION
      An inverse function has a source for every target, but a source might have 0, 1 or more targets.

      Obeys the constraints isMandatorySource(), isSingleSource().

      Similar types:

    • INVERSE_PARTIAL_FUNCTION

      public static final MappingType INVERSE_PARTIAL_FUNCTION

    • FOURTEEN

      public static final MappingType FOURTEEN

    • MULTI_FUNCTION

      public static final MappingType MULTI_FUNCTION

  • Method Details

    • values

      public static MappingType[] values()
      Returns an array containing the constants of this enum type, in the order they are declared.
      Returns:
      an array containing the constants of this enum type, in the order they are declared

    • valueOf

      public static MappingType valueOf(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:
      IllegalArgumentException - if this enum type has no constant with the specified name
      NullPointerException - if the argument is null

    • inverse

      public MappingType inverse()

    • 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.