ai.grakn.graql.internal.gremlin.fragment

Interface Fragment

public interface Fragment

represents a graph traversal, with one start point and optionally an end point

A fragment is composed of four things:

• A gremlin traversal function, that takes a gremlin traversal and appends some new gremlin steps
• A starting variable name, where the gremlin traversal must start from
• An optional ending variable name, if the gremlin traversal navigates to a new Graql variable
• A priority, that describes how efficient this traversal is to help with ordering the traversals

Variable names refer to Graql variables. Some of these variable names may be randomly-generated UUIDs, such as for castings.

A Fragment is usually contained in a EquivalentFragmentSet, which contains multiple fragments describing the different directions the traversal can be followed in, with different starts and ends.

A gremlin traversal is created from a Query by appending together fragments in order of priority, one from each EquivalentFragmentSet describing the Query.

Method Summary

Modifier and Type	Method and Description
void	applyTraversal(org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversal<org.apache.tinkerpop.gremlin.structure.Vertex,org.apache.tinkerpop.gremlin.structure.Vertex> traversal)
double	fragmentCost(double previousCost)
Set<VarName>	getDependencies()
Optional<VarName>	getEnd()
EquivalentFragmentSet	getEquivalentFragmentSet()
String	getName() The name of the fragment
VarName	getStart()
java.util.stream.Stream<VarName>	getVariableNames() Get all variable names in the fragment - the start and end (if present)
default boolean	isStartingFragment() A starting fragment is a fragment that can start a traversal.
void	setEquivalentFragmentSet(EquivalentFragmentSet equivalentFragmentSet)

Method Detail

getEquivalentFragmentSet

EquivalentFragmentSet getEquivalentFragmentSet()

Returns:

the EquivalentFragmentSet that contains this Fragment

setEquivalentFragmentSet

void setEquivalentFragmentSet(EquivalentFragmentSet equivalentFragmentSet)

Parameters:

equivalentFragmentSet - the EquivalentFragmentSet that contains this Fragment

applyTraversal

void applyTraversal(org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversal<org.apache.tinkerpop.gremlin.structure.Vertex,org.apache.tinkerpop.gremlin.structure.Vertex> traversal)

Parameters:

traversal - the traversal to extend with this Fragment

getName

String getName()

The name of the fragment

getStart

VarName getStart()

Returns:

the variable name that this fragment starts from in the query

getEnd

Optional<VarName> getEnd()

Returns:

the variable name that this fragment ends at in the query, if this query has an end variable

getDependencies

Set<VarName> getDependencies()

Returns:

the variable names that this fragment requires to have already been visited

getVariableNames

java.util.stream.Stream<VarName> getVariableNames()

Get all variable names in the fragment - the start and end (if present)

isStartingFragment

default boolean isStartingFragment()

A starting fragment is a fragment that can start a traversal. If any other fragment is present that refers to the same variable, the starting fragment can be omitted.

fragmentCost

double fragmentCost(double previousCost)