org.modeshape.jcr.query.optimize.RemoveEmptyAccessNodes Maven / Gradle / Ivy
/*
* 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.PlanNode;
import org.modeshape.jcr.query.plan.PlanNode.Property;
import org.modeshape.jcr.query.plan.PlanNode.Type;
/**
* An {@link OptimizerRule optimizer rule} that removes any ACCESS nodes that are known to never return any tuples because of
* conflicting constraints.
*/
@Immutable
public class RemoveEmptyAccessNodes implements OptimizerRule {
public static final RemoveEmptyAccessNodes INSTANCE = new RemoveEmptyAccessNodes();
@Override
public PlanNode execute( QueryContext context,
PlanNode plan,
LinkedList ruleStack ) {
// Find all access nodes ...
for (PlanNode access : plan.findAllAtOrBelow(Type.ACCESS)) {
if (access.getProperty(Property.ACCESS_NO_RESULTS, Boolean.class)) {
// This node has conflicting constraints and will never return any results ...
// TODO: implement this rule.
// At least the QueryProcessor looks for this property and always creates a NoResultsComponent,
// saving some work. But implementing this rule will make queries more efficient.
}
}
return plan;
}
@Override
public String toString() {
return getClass().getSimpleName();
}
}
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