Module org.apache.jena.arq

Package org.apache.jena.sparql.algebra.optimize

Class TransformPathFlattenAlgebra

java.lang.Object

org.apache.jena.sparql.algebra.TransformCopy

org.apache.jena.sparql.algebra.optimize.TransformPathFlattenAlgebra

All Implemented Interfaces:

Transform

public class TransformPathFlattenAlgebra
extends TransformCopy

The path transformation step mostly per the SPARQL 1.1 spec with some enhancement e.g. expanding alternative paths into unions.

It does not necessarily produce very nice execution structures so ARQ uses a functionally equivalent, but different, transformation, see TransformPathFlatten, although that transformation covers fewer cases than this. Some of the rough edges of this transform are however smoothed out by subsequent application of other transforms e.g. TransformMergeBGPs in the standard optimiser (see OptimizerStd)

However, for users who are using property paths in their queries heavily there may be benefits to using this transform over the default one. The ARQ.optPathFlattenAlgebra symbol can be set in an ARQ context to enable this transform in preference to the default transform.

Field Summary

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

COPY_ALWAYS, COPY_ONLY_ON_CHANGE

Constructor Summary

Constructors

Constructor	Description
TransformPathFlattenAlgebra()

Method Summary

Modifier and Type	Method	Description
static void	resetForTest()	Testing use only.
Op	transform(OpPath opPath)

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, transform

Methods inherited from class java.lang.Object

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

Constructor Details

TransformPathFlattenAlgebra

public TransformPathFlattenAlgebra()

Method Details

resetForTest

public static void resetForTest()

Testing use only.

transform

public Op transform(OpPath opPath)

Specified by:

transform in interface Transform

Overrides:

transform in class TransformCopy