org.apache.jena.sdb.compiler

Class TransformOptimizeSubqueryFragments

java.lang.Object

org.apache.jena.sparql.algebra.TransformCopy

org.apache.jena.sdb.compiler.TransformOptimizeSubqueryFragments

All Implemented Interfaces:

Transform

public class TransformOptimizeSubqueryFragments
extends TransformCopy

For large datasets, the performance of the OPTIONAL joins and MINUS in SQL can suffer, as the subqueries generate large views which are expensive to join. This optimizer transforms the algebra to insert the restrictions from outside of the optional subquery, reducing the amount of data that has to be joined. By reducing the amount of data that is considered in the LEFT JOIN/MINUS operations, the efficiency and performance of such constructs is greatly improved in most cases.

Field Summary

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

COPY_ALWAYS, COPY_ONLY_ON_CHANGE

Method Summary

Modifier and Type	Method and Description
static Op	transform(Op op) Static method to run the transformer (needs to keep track of visited nodes)
Op	transform(OpJoin opJoin, Op opLeft, Op opRight) Run transformation on joins
Op	transform(OpLeftJoin opLeftJoin, Op opLeft, Op opRight) Run transformation on leftjoins
Op	transform(OpMinus opMinus, Op opLeft, Op opRight) Run transformation on minus
Op	transform(OpUnion opUnion, Op opLeft, Op opRight) Run transformation on unions

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

Methods inherited from class java.lang.Object

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

Method Detail

transform

public static Op transform(Op op)

Static method to run the transformer (needs to keep track of visited nodes)

transform

public Op transform(OpJoin opJoin,
                    Op opLeft,
                    Op opRight)

Run transformation on joins

Specified by:

transform in interface Transform

Overrides:

transform in class TransformCopy

transform

public Op transform(OpLeftJoin opLeftJoin,
                    Op opLeft,
                    Op opRight)

Run transformation on leftjoins

Specified by:

transform in interface Transform

Overrides:

transform in class TransformCopy

transform

public Op transform(OpMinus opMinus,
                    Op opLeft,
                    Op opRight)

Run transformation on minus

Specified by:

transform in interface Transform

Overrides:

transform in class TransformCopy

transform

public Op transform(OpUnion opUnion,
                    Op opLeft,
                    Op opRight)

Run transformation on unions

Specified by:

transform in interface Transform

Overrides:

transform in class TransformCopy