| /* |
| * Copyright 2009-2010 by The Regents of the University of California |
| * 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 from |
| * |
| * 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 edu.uci.ics.hyracks.algebricks.rewriter.rules; |
| |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.Set; |
| |
| import org.apache.commons.lang3.mutable.Mutable; |
| |
| import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException; |
| import edu.uci.ics.hyracks.algebricks.common.utils.Pair; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalOperator; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.IOptimizationContext; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalExpressionTag; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalOperatorTag; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator; |
| import edu.uci.ics.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule; |
| |
| /** |
| * Removes duplicate variables from a group-by operator's decor list. |
| */ |
| public class RemoveRedundantGroupByDecorVars implements IAlgebraicRewriteRule { |
| |
| private final Set<LogicalVariable> vars = new HashSet<LogicalVariable>(); |
| |
| @Override |
| public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context) { |
| AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue(); |
| if (op.getOperatorTag() != LogicalOperatorTag.GROUP) { |
| return false; |
| } |
| if (context.checkIfInDontApplySet(this, op)) { |
| return false; |
| } |
| vars.clear(); |
| |
| boolean modified = false; |
| GroupByOperator groupOp = (GroupByOperator) op; |
| Iterator<Pair<LogicalVariable, Mutable<ILogicalExpression>>> iter = groupOp.getDecorList().iterator(); |
| while (iter.hasNext()) { |
| Pair<LogicalVariable, Mutable<ILogicalExpression>> decor = iter.next(); |
| if (decor.first != null || decor.second.getValue().getExpressionTag() != LogicalExpressionTag.VARIABLE) { |
| continue; |
| } |
| VariableReferenceExpression varRefExpr = (VariableReferenceExpression) decor.second.getValue(); |
| LogicalVariable var = varRefExpr.getVariableReference(); |
| if (vars.contains(var)) { |
| iter.remove(); |
| modified = true; |
| } else { |
| vars.add(var); |
| } |
| } |
| if (modified) { |
| context.addToDontApplySet(this, op); |
| } |
| return modified; |
| } |
| |
| @Override |
| public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) throws AlgebricksException { |
| return false; |
| } |
| } |