org.apache.jena.sparql.algebra.optimize

Class TransformTopN

java.lang.Object

org.apache.jena.sparql.algebra.TransformCopy

org.apache.jena.sparql.algebra.optimize.TransformTopN

All Implemented Interfaces:

Transform

public class TransformTopN
extends TransformCopy

Optimization that changes queries that uses OFFSET/LIMIT and ORDER BY to execute using Top N: i.e. while executing, keep only the top N items seen. This avoids full sort of the whole results, saving space and time.

Field Summary

Fields

Modifier and Type	Field and Description
static Symbol	externalSortBufferSize

Fields inherited from class org.apache.jena.sparql.algebra.TransformCopy

COPY_ALWAYS, COPY_ONLY_ON_CHANGE

Constructor Summary

Constructors

Constructor and Description
TransformTopN()

Method Summary

Modifier and Type	Method and Description
Op	transform(OpSlice opSlice, Op inSubOp)

Methods inherited from class org.apache.jena.sparql.algebra.TransformCopy

transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform, transform

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

externalSortBufferSize

public static final Symbol externalSortBufferSize

Constructor Detail

TransformTopN

public TransformTopN()

Method Detail

transform

public Op transform(OpSlice opSlice,
                    Op inSubOp)

Specified by:

transform in interface Transform

Overrides:

transform in class TransformCopy