org.apache.tinkerpop.gremlin.process.traversal

Interface TraversalSideEffects

All Superinterfaces:

Cloneable, Serializable

public interface TraversalSideEffects
extends Cloneable, Serializable

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)

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	TraversalSideEffects.Exceptions

Field Summary

Fields

Modifier and Type	Field and Description
static String	SIDE_EFFECTS

Method Summary

Modifier and Type	Method and Description
TraversalSideEffects	clone() Cloning is used to duplicate the sideEffects typically in OLAP environments.
default <V> void	forEach(BiConsumer<String,V> biConsumer)
<V> Optional<V>	get(String key) Get the sideEffect associated with the provided key.
default <V> V	getOrCreate(String key, Supplier<V> orCreate) If the sideEffect contains an object associated with the key, return it.
<V> Optional<Supplier<V>>	getRegisteredSupplier(String key) Get the registered Supplier associated with the specified key.
<S> Optional<Supplier<S>>	getSackInitialValue() If sacks are enabled, get the initial value of the Traverser sack.
<S> Optional<UnaryOperator<S>>	getSackSplitOperator() If sacks are enabled and a split operator has been specified, then get it.
Set<String>	keys() The keys of the sideEffect which includes registered Supplier keys.
void	mergeInto(TraversalSideEffects sideEffects) Add the current TraversalSideEffects data and suppliers to the provided TraversalSideEffects.
void	registerSupplier(String key, Supplier supplier) Register a Supplier with the provided key.
default void	registerSupplierIfAbsent(String key, Supplier supplier) A helper method to register a Supplier if it has not already been registered.
void	remove(String key) Remove both the value and registered Supplier associated with provided key.
void	set(String key, Object value) Set the specified key to the specified value.
void	setLocalVertex(Vertex vertex) In a distributed GraphComputer traversal, the sideEffects of the traversal are not a single object within a single JVM.
<S> void	setSack(Supplier<S> initialValue, Optional<UnaryOperator<S>> splitOperator) Set the initial value of each Traverser "sack" along with the operator for splitting sacks.

Field Detail

SIDE_EFFECTS

static final String SIDE_EFFECTS

See Also:

Constant Field Values

Method Detail

set

void set(String key,
         Object value)

Set the specified key to the specified value. If a Supplier is provided, it is NOT assumed to be a supplier as set by registerSupplier().

Parameters:

key - the key

value - the value

get

<V> Optional<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 in an Optional. 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.

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().

Returns:

the keys of the sideEffect

registerSupplier

void registerSupplier(String key,
                      Supplier supplier)

Register a Supplier with the provided key. When sideEffects get() are called, if no object exists and there exists a registered supplier for the key, the object is generated. Registered suppliers are used for the lazy generation of sideEffect data.

Parameters:

key - the key to register the supplier with

supplier - the supplier that will generate an object when get() is called if it hasn't already been created

getRegisteredSupplier

<V> Optional<Supplier<V>> getRegisteredSupplier(String key)

Get the registered Supplier associated with the specified key.

Type Parameters:

V - The object type of the supplier

Parameters:

key - the key associated with the supplier

Returns:

A non-empty optional if the supplier exists

registerSupplierIfAbsent

default void registerSupplierIfAbsent(String key,
                                      Supplier supplier)

A helper method to register a Supplier if it has not already been registered.

Parameters:

key - the key of the supplier to register

supplier - the supplier to register if the key has not already been registered

setSack

<S> void setSack(Supplier<S> initialValue,
                 Optional<UnaryOperator<S>> splitOperator)

Set the initial value of each Traverser "sack" along with the operator for splitting sacks. If no operator is provided, then a direct memory copy is assumed (this is typically good for primitive types and strings).

Type Parameters:

S - the sack type

Parameters:

initialValue - the initial value supplier of the traverser sack

splitOperator - the split operator for splitting traverser sacks

getSackInitialValue

<S> Optional<Supplier<S>> getSackInitialValue()

If sacks are enabled, get the initial value of the Traverser sack.

Type Parameters:

S - the sack type

Returns:

the supplier of the initial value of the traverser sack

getSackSplitOperator

<S> Optional<UnaryOperator<S>> getSackSplitOperator()

If sacks are enabled and a split operator has been specified, then get it. The split operator is used to split a stack when a bifurcation in a Traverser happens.

Type Parameters:

S - the sack type

Returns:

the operator for splitting a traverser sack

getOrCreate

default <V> V getOrCreate(String key,
                          Supplier<V> orCreate)

If the sideEffect contains an object associated with the key, return it. Else if a "with" supplier exists for the key, generate the object, store it in the sideEffects and return the object. Else use the provided supplier to generate the object, store it in the sideEffects and return the object. Note that if the orCreate supplier is used, it is NOT registered as a Supplier.

Type Parameters:

V - the return type of the object

Parameters:

key - the key of the object to get

orCreate - if the object doesn't exist as an object or suppliable object, then generate it with the specified supplier

Returns:

the object that is either retrieved, generated, or supplier via orCreate

forEach

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

setLocalVertex

void setLocalVertex(Vertex vertex)

In a distributed GraphComputer traversal, the sideEffects of the traversal are not a single object within a single JVM. Instead, the sideEffects are distributed across the graph and the pieces are stored on the computing vertices. This method is necessary to call when the Traversal is processing the Traversers at a particular Vertex.

Parameters:

vertex - the vertex where the traversal is currently executing.

clone

TraversalSideEffects clone()

Cloning is used to duplicate the sideEffects typically in OLAP environments.

Returns:

The cloned sideEffects

mergeInto

void mergeInto(TraversalSideEffects sideEffects)

Add the current TraversalSideEffects data and suppliers to the provided TraversalSideEffects.

Parameters:

sideEffects - the sideEffects to add this traversal's sideEffect data to.