| /* |
| * 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.hyracks.algebricks.rewriter.rules; |
| |
| import java.util.List; |
| |
| import org.apache.commons.lang3.mutable.Mutable; |
| |
| import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException; |
| import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator; |
| import org.apache.hyracks.algebricks.core.algebra.base.ILogicalPlan; |
| import org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext; |
| import org.apache.hyracks.algebricks.core.algebra.base.LogicalOperatorTag; |
| import org.apache.hyracks.algebricks.core.algebra.base.LogicalVariable; |
| import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator; |
| import org.apache.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator; |
| import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule; |
| |
| /** |
| * This rule lift out the aggregate operator out from a group-by operator |
| * if the gby operator groups-by on empty key, e.g., the group-by variables are empty. |
| * |
| * @author yingyib |
| */ |
| public class EliminateGroupByEmptyKeyRule implements IAlgebraicRewriteRule { |
| |
| @Override |
| public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) throws AlgebricksException { |
| return false; |
| } |
| |
| @Override |
| public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context) |
| throws AlgebricksException { |
| AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue(); |
| if (op.getOperatorTag() != LogicalOperatorTag.GROUP) { |
| return false; |
| } |
| GroupByOperator groupOp = (GroupByOperator) op; |
| List<LogicalVariable> groupVars = groupOp.getGbyVarList(); |
| if (groupVars.size() > 0) { |
| return false; |
| } |
| List<ILogicalPlan> nestedPlans = groupOp.getNestedPlans(); |
| if (nestedPlans.size() > 1) { |
| return false; |
| } |
| ILogicalPlan nestedPlan = nestedPlans.get(0); |
| if (nestedPlan.getRoots().size() > 1) { |
| return false; |
| } |
| Mutable<ILogicalOperator> topOpRef = nestedPlan.getRoots().get(0); |
| ILogicalOperator topOp = nestedPlan.getRoots().get(0).getValue(); |
| Mutable<ILogicalOperator> nestedTupleSourceRef = getNestedTupleSourceReference(topOpRef); |
| /** |
| * connect nested top op into the plan |
| */ |
| opRef.setValue(topOp); |
| /** |
| * connect child op into the plan |
| */ |
| nestedTupleSourceRef.setValue(groupOp.getInputs().get(0).getValue()); |
| return true; |
| } |
| |
| private Mutable<ILogicalOperator> getNestedTupleSourceReference(Mutable<ILogicalOperator> nestedTopOperatorRef) { |
| Mutable<ILogicalOperator> currentOpRef = nestedTopOperatorRef; |
| while (currentOpRef.getValue().getInputs() != null && currentOpRef.getValue().getInputs().size() > 0) { |
| currentOpRef = currentOpRef.getValue().getInputs().get(0); |
| } |
| return currentOpRef; |
| } |
| |
| } |