Package org.apache.tinkerpop.gremlin.gql

Class ExtensionStep

java.lang.Object

org.apache.tinkerpop.gremlin.gql.ExtensionStep

public final class ExtensionStep
extends Object

A single join step in a compiled GqlMatchPlan. An ExtensionStep describes how to extend a partial match by traversing one edge from an already-bound vertex (the anchor) to a new candidate vertex.

The planner emits one ExtensionStep per QueryEdge in the QueryGraph, ordered so that the anchor variable is always bound before the step is executed.

Fields:

• anchorVariable — the variable name of the already-bound vertex from which traversal begins; never null
• edgeLabel — optional label constraint on the edge; null means any label is accepted
• direction — traversal direction relative to the anchor vertex
• edgeVariable — optional variable name to which the matching edge is bound
• targetLabel — optional label constraint on the target vertex
• targetVariable — optional variable name to which the target vertex is bound
• targetPredicates — property equality predicates on the target vertex, derived from the inline filter map on the corresponding QueryVertex
• estimatedCost — static selectivity estimate set by the planner; lower values indicate a more selective step that should be tried first when multiple steps are simultaneously eligible. Computed as min(edgeLabelCount, indexedPropertyCount).

At runtime, the executor maintains adaptive counters (recordAttempt() / recordHit()) so that selectivityRatio() reflects observed throughput. The executor uses this ratio — with estimatedCost as a tiebreaker — to choose among simultaneously eligible steps.

Constructor Summary

Constructors

Constructor	Description
ExtensionStep(String anchorVariable, String edgeLabel, Direction direction, String edgeVariable, String targetLabel, String targetVariable)
ExtensionStep(String anchorVariable, String edgeLabel, Direction direction, String edgeVariable, String targetLabel, String targetVariable, List<PropertyPredicate> targetPredicates)
ExtensionStep(String anchorVariable, String edgeLabel, Direction direction, String edgeVariable, String targetLabel, String targetVariable, List<PropertyPredicate> targetPredicates, long estimatedCost)
ExtensionStep(String anchorVariable, String edgeLabel, Direction direction, String edgeVariable, List<PropertyPredicate> edgePredicates, String targetLabel, String targetVariable, List<PropertyPredicate> targetPredicates, long estimatedCost)

Method Summary

Modifier and Type	Method	Description
String	getAnchorVariable()	The variable name of the already-bound vertex used as the starting point for this step.
Direction	getDirection()	The traversal direction from the anchor vertex.
String	getEdgeLabel()	The edge label constraint, or null for any label.
List<PropertyPredicate>	getEdgePredicates()	Property equality predicates that the traversed edge must satisfy.
String	getEdgeVariable()	The variable name to which the matching edge is bound, or null.
long	getEstimatedCost()	Static cost estimate set by the planner.
String	getTargetLabel()	The label constraint on the target vertex, or null for any label.
List<PropertyPredicate>	getTargetPredicates()	Property equality predicates that the target vertex must satisfy, derived from the inline filter map on the target QueryVertex.
String	getTargetVariable()	The variable name to which the matching target vertex is bound, or null.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

ExtensionStep

public ExtensionStep(String anchorVariable,
 String edgeLabel,
 Direction direction,
 String edgeVariable,
 List<PropertyPredicate> edgePredicates,
 String targetLabel,
 String targetVariable,
 List<PropertyPredicate> targetPredicates,
 long estimatedCost)

ExtensionStep

public ExtensionStep(String anchorVariable,
 String edgeLabel,
 Direction direction,
 String edgeVariable,
 String targetLabel,
 String targetVariable,
 List<PropertyPredicate> targetPredicates,
 long estimatedCost)

ExtensionStep

public ExtensionStep(String anchorVariable,
 String edgeLabel,
 Direction direction,
 String edgeVariable,
 String targetLabel,
 String targetVariable,
 List<PropertyPredicate> targetPredicates)

ExtensionStep

public ExtensionStep(String anchorVariable,
 String edgeLabel,
 Direction direction,
 String edgeVariable,
 String targetLabel,
 String targetVariable)

Method Details

getAnchorVariable

public String getAnchorVariable()

The variable name of the already-bound vertex used as the starting point for this step.

getEdgeLabel

public String getEdgeLabel()

The edge label constraint, or null for any label.

getDirection

public Direction getDirection()

The traversal direction from the anchor vertex.

getEdgeVariable

public String getEdgeVariable()

The variable name to which the matching edge is bound, or null.

getEdgePredicates

public List<PropertyPredicate> getEdgePredicates()

Property equality predicates that the traversed edge must satisfy. Empty if no filter was specified on the edge pattern element.

getTargetLabel

public String getTargetLabel()

The label constraint on the target vertex, or null for any label.

getTargetVariable

public String getTargetVariable()

The variable name to which the matching target vertex is bound, or null.

getTargetPredicates

public List<PropertyPredicate> getTargetPredicates()

Property equality predicates that the target vertex must satisfy, derived from the inline filter map on the target QueryVertex. Empty if no filter was specified.

getEstimatedCost

public long getEstimatedCost()

Static cost estimate set by the planner. Lower values indicate a more selective step. Computed as min(edgeLabelCount, indexedPropertyCount) at plan compile time.

toString

public String toString()

Overrides:

toString in class Object