Package org.apache.tinkerpop.gremlin.process.traversal

Interface TraversalSideEffects

All Superinterfaces:
AutoCloseable, Cloneable, Serializable
public interface TraversalSideEffects extends Cloneable, Serializable, AutoCloseable
A Traversal can maintain global sideEffects. Unlike Traverser "sacks" which are local sideEffects, TraversalSideEffects are accessible by all Traverser instances within the Traversal.
Author:
Marko A. Rodriguez (http://markorodriguez.com)

  • Method Details

    • exists

      default boolean exists(String key)
      Return true if the key is a registered side-effect.
      Parameters:
      key - the key to check for existence
      Returns:
      whether the key exists or not

    • get

      <V> V get(String key) throws IllegalArgumentException
      Get the sideEffect associated with the provided key. If the sideEffect contains an object for the key, return it. Else if the sideEffect has a registered Supplier for that key, generate the object, store the object in the sideEffects, and return it.
      Type Parameters:
      V - the type of the value to retrieve
      Parameters:
      key - the key to get the value for
      Returns:
      the value associated with key
      Throws:
      IllegalArgumentException - if the key does not reference an object or a registered supplier.

    • set

      void set(String key, Object value) throws IllegalArgumentException
      Set the specified key to the specified value. This method should not be used in a distributed environment. Instead, use add(String, Object). This method is only safe when there is only one representation of the side-effect and thus, not distributed across threads or machines.
      Parameters:
      key - the key they key of the side-effect
      value - the value the new value for the side-effect
      Throws:
      IllegalArgumentException - if the key does not reference a registered side-effect.

    • remove

      void remove(String key)
      Remove both the value and registered Supplier associated with provided key.
      Parameters:
      key - the key of the value and registered supplier to remove

    • keys

      Set<String> keys()
      The keys of the sideEffect which includes registered Supplier keys. In essence, that which is possible to get(String).
      Returns:
      the keys of the sideEffect

    • close

      default void close() throws Exception
      Invalidate the side effect cache for traversal.
      Specified by:
      close in interface AutoCloseable
      Throws:
      Exception

    • isEmpty

      default boolean isEmpty()
      Determines if there are any side-effects to be retrieved.

    • register

      <V> void register(String key, Supplier<V> initialValue, BinaryOperator<V> reducer)
      Register a side-effect with the TraversalSideEffects providing a Supplier and a BinaryOperator. If a null value is provided for the supplier or reducer, then it no supplier or reducer is registered.
      Type Parameters:
      V - the type of the side-effect value
      Parameters:
      key - the key of the side-effect value
      initialValue - the initial value supplier
      reducer - the reducer to use for merging a distributed side-effect value into a single value

    • registerIfAbsent

      <V> void registerIfAbsent(String key, Supplier<V> initialValue, BinaryOperator<V> reducer)
      Register a side-effect with the TraversalSideEffects providing a Supplier and a BinaryOperator. The registration will only overwrite a supplier or reducer if no supplier or reducer existed prior. If a null value is provided for the supplier or reducer, then it no supplier or reducer is registered.
      Type Parameters:
      V - the type of the side-effect value
      Parameters:
      key - the key of the side-effect value
      initialValue - the initial value supplier
      reducer - the reducer to use for merging a distributed side-effect value into a single value

    • getReducer

      <V> BinaryOperator<V> getReducer(String key) throws IllegalArgumentException
      Get the reducer associated with the side-effect key. If no reducer was registered, then Operator.assign is provided.
      Type Parameters:
      V - the type of the side-effect value
      Parameters:
      key - the key of the side-effect
      Returns:
      the registered reducer
      Throws:
      IllegalArgumentException - if no side-effect exists for the provided key

    • getSupplier

      <V> Supplier<V> getSupplier(String key) throws IllegalArgumentException
      Get the supplier associated with the side-effect key. If no supplier was registered, then ConstantSupplier is provided.
      Type Parameters:
      V - the type of the side-effect value
      Parameters:
      key - the key of the side-effect
      Returns:
      the registered supplier
      Throws:
      IllegalArgumentException - if no side-effect exists for the provided key

    • add

      void add(String key, Object value) throws IllegalArgumentException
      Add a value to the global side-effect value. This should be used by steps to ensure that side-effects are merged properly in a distributed environment. set(String, Object) should only be used in single-threaded systems or by a master traversal in a distributed environment.
      Parameters:
      key - the key of the side-effect.
      value - the partital value (to be merged) of the side-effect.
      Throws:
      IllegalArgumentException - if no side-effect exists for the provided key

    • setSack

      <S> void setSack(Supplier<S> initialValue, UnaryOperator<S> splitOperator, BinaryOperator<S> mergeOperator)
      Set the initial value of each Traverser "sack" along with the operators for splitting and merging sacks. If no split operator is provided, then a direct memory copy is assumed (this is typically good for primitive types and strings). If no merge operator is provided, then traversers with sacks will not be merged.
      Type Parameters:
      S - the sack type
      Parameters:
      initialValue - the initial value supplier of the traverser sack
      splitOperator - the split operator for splitting traverser sacks
      mergeOperator - the merge operator for merging traverser sacks

    • getSackInitialValue

      <S> Supplier<S> getSackInitialValue()
      If sacks are enabled, get the initial value of the Traverser sack. If its not enabled, then null is returned.
      Type Parameters:
      S - the sack type
      Returns:
      the supplier of the initial value of the traverser sack

    • getSackSplitter

      <S> UnaryOperator<S> getSackSplitter()
      If sacks are enabled and a split operator has been specified, then get it (else get null). The split operator is used to split a sack when a bifurcation in a Traverser happens.
      Type Parameters:
      S - the sack type
      Returns:
      the operator for splitting a traverser sack

    • getSackMerger

      <S> BinaryOperator<S> getSackMerger()
      If sacks are enabled and a merge function has been specified, then get it (else get null). The merge function is used to merge two sacks when two Traversers converge.
      Type Parameters:
      S - the sack type
      Returns:
      the operator for merging two traverser sacks

    • forEach

      default <V> void forEach(BiConsumer<String,V> biConsumer)

    • clone

      TraversalSideEffects clone()
      Cloning is used to duplicate the sideEffects typically in distributed execution environments.
      Returns:
      The cloned sideEffects

    • mergeInto

      void mergeInto(TraversalSideEffects sideEffects)
      Add the current TraversalSideEffects values, suppliers, and reducers to the provided TraversalSideEffects. The implementation should (under the hood), use registerIfAbsent(String, Supplier, BinaryOperator) so that if the argument TraversalSideEffects already has a registered supplier or binary operator, then don't overwrite it.
      Parameters:
      sideEffects - the sideEffects to add this traversal's sideEffect data to.