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

Interface TraversalSideEffects

All Superinterfaces:

AutoCloseable, Cloneable, Serializable

All Known Implementing Classes:

DefaultTraversalSideEffects, EmptyTraversalSideEffects, MemoryTraversalSideEffects

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)

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	TraversalSideEffects.Exceptions

Method Summary

Modifier and Type	Method	Description
void	add(String key, Object value)	Add a value to the global side-effect value.
TraversalSideEffects	clone()	Cloning is used to duplicate the sideEffects typically in distributed execution environments.
default void	close()	Invalidate the side effect cache for traversal.
default boolean	exists(String key)	Return true if the key is a registered side-effect.
default <V> void	forEach(BiConsumer<String,V> biConsumer)
<V> V	get(String key)	Get the sideEffect associated with the provided key.
<V> BinaryOperator<V>	getReducer(String key)	Get the reducer associated with the side-effect key.
<S> Supplier<S>	getSackInitialValue()	If sacks are enabled, get the initial value of the Traverser sack.
<S> BinaryOperator<S>	getSackMerger()	If sacks are enabled and a merge function has been specified, then get it (else get null).
<S> UnaryOperator<S>	getSackSplitter()	If sacks are enabled and a split operator has been specified, then get it (else get null).
<V> Supplier<V>	getSupplier(String key)	Get the supplier associated with the side-effect key.
default boolean	isEmpty()	Determines if there are any side-effects to be retrieved.
Set<String>	keys()	The keys of the sideEffect which includes registered Supplier keys.
void	mergeInto(TraversalSideEffects sideEffects)	Add the current TraversalSideEffects values, suppliers, and reducers to the provided TraversalSideEffects.
<V> void	register(String key, Supplier<V> initialValue, BinaryOperator<V> reducer)	Register a side-effect with the TraversalSideEffects providing a Supplier and a BinaryOperator.
<V> void	registerIfAbsent(String key, Supplier<V> initialValue, BinaryOperator<V> reducer)	Register a side-effect with the TraversalSideEffects providing a Supplier and a BinaryOperator.
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.
<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.

Method Detail

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.