| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.pig.newplan.logical.rules; |
| |
| import java.util.Iterator; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.pig.impl.logicalLayer.FrontendException; |
| import org.apache.pig.impl.util.MultiMap; |
| import org.apache.pig.newplan.Operator; |
| import org.apache.pig.newplan.OperatorPlan; |
| import org.apache.pig.newplan.OperatorSubPlan; |
| import org.apache.pig.newplan.logical.expression.ConstantExpression; |
| import org.apache.pig.newplan.logical.expression.LogicalExpressionPlan; |
| import org.apache.pig.newplan.logical.relational.LOCogroup; |
| import org.apache.pig.newplan.logical.relational.LogicalPlan; |
| import org.apache.pig.newplan.logical.relational.LogicalRelationalOperator; |
| import org.apache.pig.newplan.optimizer.Rule; |
| import org.apache.pig.newplan.optimizer.Transformer; |
| |
| /** |
| * Rule: If a LOCogroup is 'group all', set the parallelism to 1, |
| * or in general - if the group-by expression is just a constant |
| * then set parallelism to 1 |
| * LogicalExpressionSimplifier could be used to convert an expression |
| * with constants into a single ConstantExpression |
| */ |
| |
| public class GroupByConstParallelSetter extends Rule { |
| |
| public GroupByConstParallelSetter(String n){ |
| super(n, false); |
| } |
| |
| @Override |
| public Transformer getNewTransformer() { |
| return new GroupAllParallelSetterTransformer(); |
| } |
| private final static Log log = LogFactory.getLog(GroupByConstParallelSetter.class); |
| |
| public class GroupAllParallelSetterTransformer extends Transformer { |
| |
| @Override |
| public boolean check(OperatorPlan matched) throws FrontendException { |
| LOCogroup group = (LOCogroup)matched.getSources().get(0); |
| MultiMap<Integer, LogicalExpressionPlan> explPlans = |
| group.getExpressionPlans(); |
| //check if the expression plan consist of just a ConstantExpression |
| for(LogicalExpressionPlan ep : explPlans.values()){ |
| Iterator<Operator> op_iter = ep.getOperators(); |
| if(op_iter.hasNext()){ |
| //return false if the ExpressionOperator is not |
| // a ConstantExpression |
| if(! (op_iter.next() instanceof ConstantExpression)){ |
| return false; |
| } |
| } |
| // if there is more than one ExpressionOperator, return false |
| if(op_iter.hasNext()){ |
| return false; |
| } |
| } |
| return true; |
| |
| } |
| |
| @Override |
| public void transform(OperatorPlan plan) throws FrontendException { |
| Iterator<Operator> iter = plan.getOperators(); |
| while (iter.hasNext()) { |
| Operator op = iter.next(); |
| if (op instanceof LOCogroup) { |
| LOCogroup group = (LOCogroup)op; |
| if(group.getRequestedParallelism() > 1){ |
| log.warn("Resetting parallism to 1 for the group/cogroup " + |
| group.getAlias() + |
| " as the group by expressions returns a constant"); |
| } |
| ((LOCogroup) op).setRequestedParallelism(1); |
| } |
| } |
| } |
| |
| |
| @Override |
| public OperatorPlan reportChanges() { |
| return new OperatorSubPlan(currentPlan); |
| } |
| } |
| |
| @Override |
| protected OperatorPlan buildPattern() { |
| LogicalPlan plan = new LogicalPlan(); |
| LogicalRelationalOperator op = new LOCogroup(plan); |
| plan.add(op); |
| return plan; |
| } |
| } |