/* * Copyright (C) 2010 eXo Platform SAS. * * This is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * This software is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this software; if not, write to the Free * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA, or see the FSF site: http://www.fsf.org. */ package org.xcmis.search.query.optimize; import org.xcmis.search.query.QueryExecutionContext; import org.xcmis.search.query.QueryExecutionExceptions; import org.xcmis.search.query.plan.Optimizer; import org.xcmis.search.query.plan.QueryExecutionPlan; import java.util.LinkedList; /** * Optimizer implementation that optimizes a query using a stack of rules. Subclasses can override the * {@link #populateCriteriaStack(LinkedList, QueryExecutionPlan)} method to define the stack of criteria they'd like to use, including the use of * custom criteria's. */ public class CriteriaBasedOptimizer implements Optimizer { /** * @see org.xcmis.search.query.plan.Optimizer#optimize(org.xcmis.search.query.QueryExecutionContext, org.xcmis.search.query.plan.QueryExecutionPlan) */ public QueryExecutionPlan optimize(QueryExecutionContext context, QueryExecutionPlan plan) { LinkedList<OptimizerCriteria> rules = new LinkedList<OptimizerCriteria>(); populateCriteriaStack(rules, plan); QueryExecutionExceptions problems = context.getExecutionExceptions(); while (rules.peek() != null && !problems.hasProblems()) { OptimizerCriteria nextRule = rules.poll(); plan = nextRule.execute(context, plan, rules); } return plan; } /** * Method that is used to create the initial criteria stack. This method can be overridden by subclasses * * @param ruleStack the stack where the rules should be placed; never null * @param hints the plan hints */ protected void populateCriteriaStack(LinkedList<OptimizerCriteria> criteriaStack, QueryExecutionPlan plan) { } }