/*
* ModeShape (http://www.modeshape.org)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.modeshape.jcr.query.optimize;
import java.util.LinkedList;
import org.modeshape.common.annotation.Immutable;
import org.modeshape.jcr.query.QueryContext;
import org.modeshape.jcr.query.plan.CanonicalPlanner;
import org.modeshape.jcr.query.plan.PlanHints;
import org.modeshape.jcr.query.plan.PlanNode;
import org.modeshape.jcr.query.plan.PlanNode.Type;
/**
* An {@link OptimizerRule optimizer rule} that inserts an ACCESS above each SOURCE leaf node in a query plan. This rule is often
* the first rule to run against a {@link CanonicalPlanner canonical plan} (see
* {@link RuleBasedOptimizer#populateRuleStack(LinkedList, PlanHints)}.
* <p>
* Before:
*
* <pre>
* ...
* |
* SOURCE
* </pre>
*
* After:
*
* <pre>
* ...
* |
* ACCESS
* |
* SOURCE
* </pre>
*
* </p>
*/
@Immutable
public class AddAccessNodes implements OptimizerRule {
public static final AddAccessNodes INSTANCE = new AddAccessNodes();
@Override
public PlanNode execute( QueryContext context,
PlanNode plan,
LinkedList<OptimizerRule> ruleStack ) {
// On each of the source nodes ...
for (PlanNode source : plan.findAllAtOrBelow(Type.SOURCE)) {
// The source node may have children if it is a view ...
if (source.getChildCount() != 0) continue;
// Create the ACCESS node, set the selectors, and insert above the source node ...
PlanNode access = new PlanNode(Type.ACCESS);
access.addSelectors(source.getSelectors());
source.insertAsParent(access);
}
return plan;
}
@Override
public String toString() {
return getClass().getSimpleName();
}
}