QueryEvaluationStep (Eclipse RDF4J 4.2.4)

All Known Subinterfaces:

SliceQueryEvaluationStep

All Known Implementing Classes:

BindingSetAssignmentQueryEvaluationStep, ExtensionQueryEvaluationStep, IntersectionQueryEvaluationStep, JoinQueryEvaluationStep, LeftJoinQueryEvaluationStep, MinusQueryEvaluationStep, OrderQueryEvaluationStep, ProjectionQueryEvaluationStep, RdfStarQueryEvaluationStep, ReificationRdfStarQueryEvaluationStep, ServiceQueryEvaluationStep, SliceQueryEvaluationStep.OffSetAndLimitQueryEvaluationStep, SliceQueryEvaluationStep.OnlyLimitQueryEvaluationStep, SliceQueryEvaluationStep.OnlyOffsetQueryEvaluationStep, StatementPatternQueryEvaluationStep, UnionQueryEvaluationStep, ZeroLengthPathEvaluationStep

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface QueryEvaluationStep
```
A Step that may need to be executed in a EvaluationStrategy. The evaluate method should do the minimal work required to evaluate given the bindings. As much as possible should be pre-computed (e.g. resolving constant values)

Nested Class Summary

Nested Classes
Modifier and Type	Interface	Description
`static class`	`QueryEvaluationStep.DelayedEvaluationIteration`	Deprecated, for removal: This API element is subject to removal in a future version.

Field Summary

Fields
Modifier and Type Field Description

static QueryEvaluationStep EMPTY

static EmptyIteration<BindingSet,QueryEvaluationException> EMPTY_ITERATION

Method Summary

All Methods Static Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`static QueryEvaluationStep`	`empty()`
`CloseableIteration<BindingSet,QueryEvaluationException>`	`evaluate(BindingSet bindings)`
`static QueryEvaluationStep`	`minimal(EvaluationStrategy strategy, TupleExpr expr)`	A fall back implementation that wraps a pre-existing evaluate method on a strategy
`static QueryEvaluationStep`	`wrap(QueryEvaluationStep qes, Function<CloseableIteration<BindingSet,QueryEvaluationException>,CloseableIteration<BindingSet,QueryEvaluationException>> wrap)`	Wrap an QueryEvalationStep: where we apply a function on every evaluation result of the wrapped EvaluationStep.

Field Detail

EMPTY_ITERATION

static final EmptyIteration<BindingSet,QueryEvaluationException> EMPTY_ITERATION

EMPTY
```
static final QueryEvaluationStep EMPTY
```

Method Detail
- evaluate
```
CloseableIteration<BindingSet,QueryEvaluationException> evaluate(BindingSet bindings)
```
- minimal
```
static QueryEvaluationStep minimal(EvaluationStrategy strategy,
                                   TupleExpr expr)
```
  A fall back implementation that wraps a pre-existing evaluate method on a strategy
  
  Parameters:
  
  strategy - that can evaluate the tuple expr.
  
  expr - that is going to be evaluated
  
  Returns:
  
  a thin wrapper arround the evaluation call.
- empty
```
static QueryEvaluationStep empty()
```
- wrap
```
static QueryEvaluationStep wrap(QueryEvaluationStep qes,
                                Function<CloseableIteration<BindingSet,QueryEvaluationException>,CloseableIteration<BindingSet,QueryEvaluationException>> wrap)
```
  Wrap an QueryEvalationStep: where we apply a function on every evaluation result of the wrapped EvaluationStep. Useful to add a timing function
  
  Parameters:
  
  qes - an QueryEvaluationStep that needs to return modified evaluation results
  
  wrap - the function that will do the modification
  
  Returns:
  
  a new evaluation step that executes wrap on the inner qes.