org.modeshape.jcr.query.optimize.PushProjects 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.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import org.modeshape.jcr.query.QueryContext;
import org.modeshape.jcr.query.model.Column;
import org.modeshape.jcr.query.model.SelectorName;
import org.modeshape.jcr.query.plan.PlanNode;
import org.modeshape.jcr.query.plan.PlanNode.Property;
import org.modeshape.jcr.query.plan.PlanNode.Type;
import org.modeshape.jcr.query.plan.PlanUtil;
/**
* This rule attempts to ensure the proper location of {@link Type#PROJECT} nodes. For example, every {@link Type#ACCESS} node
* needs to have a PROJECT node below it and above any other nodes (e.g., {@link Type#SELECT} or {@link Type#SOURCE} nodes). This
* rule ensures that the PROJECT exists, but it also attempts to reduce any unnecessary columns in existing PROJECT nodes.
*/
public class PushProjects implements OptimizerRule {
public static final PushProjects INSTANCE = new PushProjects();
@Override
public PlanNode execute( QueryContext context,
PlanNode plan,
LinkedList ruleStack ) {
// Find all of the ACCESS nodes to make sure there is a PROJECT ...
for (PlanNode access : plan.findAllAtOrBelow(Type.ACCESS)) {
// Find the first node that is below any LIMIT, SORT, or DUP_REMOVE ...
PlanNode parentOfProject = access;
while (parentOfProject.isOneOf(Type.LIMIT, Type.SORT, Type.DUP_REMOVE)) {
parentOfProject = parentOfProject.getParent();
}
// Is there already a PROJECT here ?
assert parentOfProject.getChildCount() == 1; // should only have one child ...
PlanNode child = parentOfProject.getFirstChild(); // should only have one child ...
if (child.is(Type.PROJECT)) {
// Check to see if there is a PROJECT above the access node ...
PlanNode accessParent = access.getParent();
if (accessParent == null || accessParent.isNot(Type.PROJECT)) continue;
// Otherwise, the parent is a PROJECT, but there is another PROJECT above the ACCESS node.
// Remove the lower PROJECT so the next code block moves the top PROJECT down below the ACCESS node ...
assert accessParent.is(Type.PROJECT);
child.extractFromParent();
child = parentOfProject.getFirstChild();
}
// If the parent of the ACCESS node is a PROJECT, then we can simply move it to here ...
PlanNode accessParent = access.getParent();
if (accessParent != null && accessParent.is(Type.PROJECT)) {
PlanNode project = accessParent;
if (project == plan) {
// The PROJECT node is the root, so the ACCESS node will be the root ...
plan = access;
access.removeFromParent();
} else {
project.extractFromParent();
}
child.insertAsParent(project);
if (plan == access) break;
// We need to make sure we have all of the columns needed for any ancestor ...
List requiredColumns = PlanUtil.findRequiredColumns(context, project);
List requiredTypes = PlanUtil.findRequiredColumnTypes(context, requiredColumns, child);
project.setProperty(Property.PROJECT_COLUMNS, requiredColumns);
project.setProperty(Property.PROJECT_COLUMN_TYPES, requiredTypes);
project.addSelectors(getSelectorsFor(requiredColumns));
continue;
}
// There is no PROJECT, so find the columns that are required by the plan above this point ...
List requiredColumns = PlanUtil.findRequiredColumns(context, child);
List requiredTypes = PlanUtil.findRequiredColumnTypes(context, requiredColumns, child);
// And insert the PROJECT ...
PlanNode projectNode = new PlanNode(Type.PROJECT);
projectNode.setProperty(Property.PROJECT_COLUMNS, requiredColumns);
projectNode.setProperty(Property.PROJECT_COLUMN_TYPES, requiredTypes);
projectNode.addSelectors(getSelectorsFor(requiredColumns));
child.insertAsParent(projectNode);
}
return plan;
}
protected Set getSelectorsFor( List columns ) {
Set selectors = new HashSet();
for (Column column : columns) {
selectors.add(column.selectorName());
}
return selectors;
}
@Override
public String toString() {
return getClass().getSimpleName();
}
}
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