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   * 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
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  package org.apache.asterix.optimizer.rules;
  
  import java.util.ArrayList;
  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.ILogicalExpression;
  import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator;
  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.AbstractBinaryJoinOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities;
  import org.apache.hyracks.algebricks.core.algebra.util.OperatorPropertiesUtil;
  import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
  
  public class PushProperJoinThroughProduct implements IAlgebraicRewriteRule {
  
      private List<LogicalVariable> usedInCond1AndMaps = new ArrayList<LogicalVariable>();
      private List<LogicalVariable> productLeftBranchVars = new ArrayList<LogicalVariable>();
  
      @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();
          LogicalOperatorTag tag1 = op.getOperatorTag();
          if (tag1 != LogicalOperatorTag.INNERJOIN && tag1 != LogicalOperatorTag.LEFTOUTERJOIN) {
              return false;
          }
          AbstractBinaryJoinOperator join1 = (AbstractBinaryJoinOperator) op;
          ILogicalExpression cond1 = join1.getCondition().getValue();
          // don't try to push a product down
          if (OperatorPropertiesUtil.isAlwaysTrueCond(cond1)) {
              return false;
          }
  
          Mutable<ILogicalOperator> opRef2 = op.getInputs().get(0);
  
          AbstractLogicalOperator op2 = (AbstractLogicalOperator) opRef2.getValue();
          while (op2.isMap()) {
              opRef2 = op2.getInputs().get(0);
              op2 = (AbstractLogicalOperator) opRef2.getValue();
          }
  
          if (op2.getOperatorTag() != LogicalOperatorTag.INNERJOIN) {
              return false;
          }
  
          InnerJoinOperator product = (InnerJoinOperator) op2;
          if (!OperatorPropertiesUtil.isAlwaysTrueCond(product.getCondition().getValue())) {
              return false;
          }
  
          usedInCond1AndMaps.clear();
          cond1.getUsedVariables(usedInCond1AndMaps);
          Mutable<ILogicalOperator> opIterRef = op.getInputs().get(0);
          ILogicalOperator opIter = opIterRef.getValue();
          do {
              VariableUtilities.getUsedVariables(opIter, usedInCond1AndMaps);
              opIterRef = opIter.getInputs().get(0);
              opIter = opIterRef.getValue();
          } while (opIter.isMap());
  
          productLeftBranchVars.clear();
          ILogicalOperator opLeft = op2.getInputs().get(0).getValue();
          VariableUtilities.getLiveVariables(opLeft, productLeftBranchVars);
  
          if (!OperatorPropertiesUtil.disjoint(usedInCond1AndMaps, productLeftBranchVars)) {
              return false;
          }
  
          // now push the operators from in between joins, too
          opIterRef = op.getInputs().get(0);
          opIter = opIterRef.getValue();
  
          Mutable<ILogicalOperator> op3Ref = product.getInputs().get(1);
          ILogicalOperator op3 = op3Ref.getValue();
  
          opRef2.setValue(op3);
          op3Ref.setValue(join1);
          opRef.setValue(product);
          return true;
      }
  }
  