com.bigdata.rdf.sparql.ast.eval

Class DGExpander

java.lang.Object

com.bigdata.rdf.sparql.ast.eval.DGExpander

All Implemented Interfaces:

IAccessPathExpander<ISPO>, Serializable

public class DGExpander
extends Object
implements IAccessPathExpander<ISPO>

Parallel subquery for a default graph access path. An expander pattern is used to ensure that the "DISTINCT SPO" constraint is applied across the subqueries rather than to each subquery individually.

Version:

$Id$

Author:

Bryan Thompson

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.apache.log4j.Logger	log

Constructor Summary

Constructors

Constructor and Description
DGExpander(int maxParallel, Collection<IV> graphs, long estimatedRangeCount)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	backchain() Add the backchainer on top of the expander.
IAccessPath<ISPO>	getAccessPath(IAccessPath<ISPO> accessPath) Return the IAccessPath that will be used to evaluate the IPredicate.
boolean	runFirst() If true, the predicate for this expander will be given priority in the join order.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

log

protected static final org.apache.log4j.Logger log

Constructor Detail

DGExpander

public DGExpander(int maxParallel,
          Collection<IV> graphs,
          long estimatedRangeCount)

Parameters:

maxParallel -

graphs - A dense ordered array of IVs.

estimatedRangeCount - The estimated range count for the subquery operation across those graphs.

Method Detail

backchain

public boolean backchain()

Description copied from interface: IAccessPathExpander

Add the backchainer on top of the expander.

Specified by:

backchain in interface IAccessPathExpander<ISPO>

Returns:

true if the backchainer should run

runFirst

public boolean runFirst()

Description copied from interface: IAccessPathExpander

If true, the predicate for this expander will be given priority in the join order.

Specified by:

runFirst in interface IAccessPathExpander<ISPO>

Returns:

true if the predicate should be run first

getAccessPath

public IAccessPath<ISPO> getAccessPath(IAccessPath<ISPO> accessPath)

Description copied from interface: IAccessPathExpander

Return the IAccessPath that will be used to evaluate the IPredicate.

Specified by:

getAccessPath in interface IAccessPathExpander<ISPO>

Parameters:

accessPath - The IAccessPath that will be used by default.

Returns:

The IAccessPath that will be used. You can return the given accessPath or you can layer additional semantics onto or otherwise override the given IAccessPath.

toString

public String toString()

Overrides:

toString in class Object