org.modeshape.jcr.query.optimize
Class PushProjects

java.lang.Object
  org.modeshape.jcr.query.optimize.PushProjects

All Implemented Interfaces:

OptimizerRule

public class PushProjects
extends Object
implements OptimizerRule

This rule attempts to ensure the proper location of PlanNode.Type.PROJECT nodes. For example, every PlanNode.Type.ACCESS node needs to have a PROJECT node below it and above any other nodes (e.g., PlanNode.Type.SELECT or PlanNode.Type.SOURCE nodes). This rule ensures that the PROJECT exists, but it also attempts to reduce any unnecessary columns in existing PROJECT nodes.

Field Summary

static PushProjects

INSTANCE

Constructor Summary

PushProjects()

Method Summary

PlanNode	execute(QueryContext context, PlanNode plan, LinkedList<OptimizerRule> ruleStack) Optimize the supplied plan using the supplied context, hints, and yet-to-be-run rules.
protected Set<SelectorName>	getSelectorsFor(List<Column> columns)
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final PushProjects INSTANCE

Constructor Detail

PushProjects

public PushProjects()

Method Detail

execute

public PlanNode execute(QueryContext context,
                        PlanNode plan,
                        LinkedList<OptimizerRule> ruleStack)

Description copied from interface: OptimizerRule

Optimize the supplied plan using the supplied context, hints, and yet-to-be-run rules.

Specified by:

execute in interface OptimizerRule

Parameters:

context - the context in which the query is being optimized; never null

plan - the plan to be optimized; never null

ruleStack - the stack of rules that will be run after this rule; never null

Returns:

the optimized plan; never null

getSelectorsFor

protected Set<SelectorName> getSelectorsFor(List<Column> columns)

toString

public String toString()

Overrides:

toString in class Object