Package it.unibz.inf.ontop.iq.planner.impl

Class AvoidJoinAboveUnionPlanner

java.lang.Object

it.unibz.inf.ontop.iq.planner.impl.AvoidJoinAboveUnionPlanner

All Implemented Interfaces:

IQOptimizer, QueryPlanner

@Singleton
public class AvoidJoinAboveUnionPlanner
extends Object
implements QueryPlanner

When an UNION appears as a child of an inner join, looks for other siblings that could be "pushed under the union".

Criteria for selecting siblings: must be leaf and must naturally join (i.e. share a variable) with the union. Example:

   JOIN
     T1(x,y)
     UNION(x,z)
       T2(x,z)
       T3(x,z)
     T4(w)
 

becomes

    JOIN
      UNION(x,z)
        JOIN
          T2(x,z)
          T1(x,y)
        JOIN
          T3(x,z)
          T1(x,y)
      T4(w)
 

TODO: shall we consider also the joining condition for pushing more siblings?

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	AvoidJoinAboveUnionPlanner.AvoidJoinAboveUnionTransformer

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AvoidJoinAboveUnionPlanner(GeneralStructuralAndSemanticIQOptimizer generalOptimizer, AvoidJoinAboveUnionPlanner.AvoidJoinAboveUnionTransformer transformer, IntermediateQueryFactory iqFactory)

Method Summary

Modifier and Type	Method	Description
protected IQ	lift(IQ query)
IQ	optimize(IQ query)	Tries to push down some inner joins under some unions.

Methods inherited from class java.lang.Object

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

Constructor Detail

AvoidJoinAboveUnionPlanner

@Inject
protected AvoidJoinAboveUnionPlanner(GeneralStructuralAndSemanticIQOptimizer generalOptimizer,
                                     AvoidJoinAboveUnionPlanner.AvoidJoinAboveUnionTransformer transformer,
                                     IntermediateQueryFactory iqFactory)

Method Detail

optimize

public IQ optimize(IQ query)

Tries to push down some inner joins under some unions. If something has been pushed, it re-applies the structural and semantic optimizations.

Specified by:

optimize in interface IQOptimizer

lift

protected IQ lift(IQ query)