com.bigdata.bop.solutions

Class SliceOp

java.lang.Object

com.bigdata.bop.CoreBaseBOp

com.bigdata.bop.BOpBase

com.bigdata.bop.PipelineOp

com.bigdata.bop.solutions.SliceOp

All Implemented Interfaces:

BOp, IPropertySet, Serializable, Cloneable

public class SliceOp
extends PipelineOp

An operator which imposes an offset/limit on a binding set pipeline.

Note: join processing typically involves concurrent processes, hence the order of the results will not be stable unless the results are sorted before applying the slice. When a slice is applied without a sort, the same query may return different results each time it is evaluated.

Note: When running on an IBigdataFederation, this operator must be imposed on the query controller so it can count the solutions as they flow through - see CoreBaseBOp.getEvaluationContext().

Note: SliceOp is safe for concurrent invocations for the same query. Multiple chunks may flow through multiple invocations of the operator so long as they use the same BOpStats object.

Version:

$Id$

Author:

Bryan Thompson

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	SliceOp.Annotations
static class	SliceOp.SliceStats Extends BOpStats to capture the state of the SliceOp.

Field Summary

Fields inherited from class com.bigdata.bop.CoreBaseBOp

DEFAULT_INITIAL_CAPACITY

Fields inherited from interface com.bigdata.bop.BOp

NOANNS, NOARGS

Constructor Summary

Constructors

Constructor and Description
SliceOp(BOp[] args, Map<String,Object> annotations) Shallow copy constructor.
SliceOp(BOp[] args, NV... annotations)
SliceOp(SliceOp op) Deep Copy constructor.

Method Summary

Methods

Modifier and Type	Method and Description
FutureTask<Void>	eval(BOpContext<IBindingSet> context) Return a FutureTask which computes the operator against the evaluation context.
long	getLimit()
long	getOffset()
SliceOp.SliceStats	newStats() Return a new object which can be used to collect statistics on the operator evaluation.

Methods inherited from class com.bigdata.bop.PipelineOp

assertAtOnceJavaHeapOp, assertMaxParallelOne, getChunkCapacity, getChunkOfChunksCapacity, getChunkTimeout, getMaxMemory, getMaxParallel, isAtOnceEvaluation, isBlockedEvaluation, isLastPassRequested, isPipelinedEvaluation, isReorderSolutions, isSharedState

Methods inherited from class com.bigdata.bop.BOpBase

__replaceArg, _clearProperty, _set, _setProperty, annotations, annotationsCopy, annotationsEqual, annotationsRef, argIterator, args, argsCopy, arity, clearAnnotations, clearProperty, deepCopy, deepCopy, get, getProperty, setArg, setProperty, setUnboundProperty, toArray, toArray

Methods inherited from class com.bigdata.bop.CoreBaseBOp

annotationsEqual, annotationsToString, annotationsToString, annotationValueToString, checkArgs, clone, equals, getEvaluationContext, getId, getProperty, getRequiredProperty, hashCode, indent, isController, mutation, shortenName, toShortString, toString, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

SliceOp

public SliceOp(SliceOp op)

Deep Copy constructor.

Parameters:

op -

SliceOp

public SliceOp(BOp[] args,
       NV... annotations)

SliceOp

public SliceOp(BOp[] args,
       Map<String,Object> annotations)

Shallow copy constructor.

Parameters:

args -

annotations -

Method Detail

getOffset

public long getOffset()

See Also:

SliceOp.Annotations.OFFSET

getLimit

public long getLimit()

See Also:

SliceOp.Annotations.LIMIT

newStats

public SliceOp.SliceStats newStats()

Description copied from class: PipelineOp

Return a new object which can be used to collect statistics on the operator evaluation. This may be overridden to return a more specific class depending on the operator.

Overrides:

newStats in class PipelineOp

eval

public FutureTask<Void> eval(BOpContext<IBindingSet> context)

Description copied from class: PipelineOp

Return a FutureTask which computes the operator against the evaluation context. The caller is responsible for executing the FutureTask (this gives them the ability to hook the completion of the computation).

Specified by:

eval in class PipelineOp

Parameters:

context - The evaluation context.

Returns:

The FutureTask which will compute the operator's evaluation.