final class ORSet[A] extends OpCrdt[DeltaOp]

Implements a 'Observed Remove Set' operation based CRDT, also called a 'OR-Set'. Elements can be added and removed any number of times. Concurrent add wins over remove.

It is not implemented as in the paper A comprehensive study of Convergent and Commutative Replicated Data Types. This is more space efficient and doesn't accumulate garbage for removed elements. It is described in the paper An optimized conflict-free replicated set The implementation is inspired by the Riak DT riak_dt_orswot.

The ORSet has a version vector that is incremented when an element is added to the set. The DC -> count pair for that increment is stored against the element as its "birth dot". Every time the element is re-added to the set, its "birth dot" is updated to that of the DC -> count version vector entry resulting from the add. When an element is removed, we simply drop it, no tombstones.

When an element exists in replica A and not replica B, is it because A added it and B has not yet seen that, or that B removed it and A has not yet seen that? In this implementation we compare the dot of the present element to the version vector in the Set it is absent from. If the element dot is not "seen" by the Set version vector, that means the other set has yet to see this add, and the item is in the merged Set. If the Set version vector dominates the dot, that means the other Set has removed this element already, and the item is not in the merged Set.

This class is immutable, i.e. "modifying" methods return a new instance.

Source
ORSet.scala
Linear Supertypes
OpCrdt[DeltaOp], AnyRef, Any
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Inherited
  1. ORSet
  2. OpCrdt
  3. AnyRef
  4. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. Protected

Type Members

  1. type D = DeltaOp
  2. type T = ORSet[A]
    Definition Classes
    → OpCrdt

Value Members

  1. def +(element: A): DeltaOp

    Adds an element to the set

  2. def -(element: A): DeltaOp

    Removes an element from the set.

  3. def add(element: A): DeltaOp

    Adds an element to the set

  4. def addAll(elems: Set[A]): DeltaOp

    Scala API: Add several elements to the set.

    Scala API: Add several elements to the set. elems must not be empty.

  5. def addAll(elems: Set[A]): DeltaOp

    Java API: Add several elements to the set.

    Java API: Add several elements to the set. elems must not be empty.

  6. def applyOperation(thatDelta: DeltaOp): ORSet[A]
    Definition Classes
    → OpCrdt
  7. def clear(): DeltaOp

    Removes all elements from the set, but keeps the history.

    Removes all elements from the set, but keeps the history. This has the same result as using #remove for each element, but it is more efficient.

  8. def contains(a: A): Boolean
  9. def elements: Set[A]

    Scala API

  10. def equals(o: Any): Boolean
    Definition Classes
    ORSet → AnyRef → Any
  11. def getElements(): Set[A]

    Java API

  12. def hashCode(): Int
    Definition Classes
    ORSet → AnyRef → Any
  13. def isEmpty: Boolean
  14. val originReplica: String
  15. def remove(element: A): DeltaOp

    Removes an element from the set.

  16. def removeAll(elems: Set[A]): DeltaOp

    Scala API: Remove several elements from the set.

    Scala API: Remove several elements from the set. elems must not be empty.

  17. def removeAll(elems: Set[A]): DeltaOp

    Java API: Remove several elements from the set.

    Java API: Remove several elements from the set. elems must not be empty.

  18. def size: Int
  19. def toString(): String
    Definition Classes
    ORSet → AnyRef → Any