content: /*
   * 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.asterix.dataflow.data.common;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.asterix.om.functions.BuiltinFunctions;
  import org.apache.commons.lang3.mutable.Mutable;
  import org.apache.commons.lang3.mutable.MutableObject;
  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.IOptimizationContext;
  import org.apache.hyracks.algebricks.core.algebra.base.LogicalVariable;
  import org.apache.hyracks.algebricks.core.algebra.expressions.AggregateFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.IMergeAggregationExpressionFactory;
  import org.apache.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
  import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
  
  public class MergeAggregationExpressionFactory implements IMergeAggregationExpressionFactory {
  
      @Override
      public ILogicalExpression createMergeAggregation(LogicalVariable originalProducedVar, ILogicalExpression expr,
              IOptimizationContext env) throws AlgebricksException {
          AggregateFunctionCallExpression agg = (AggregateFunctionCallExpression) expr;
          FunctionIdentifier fid = agg.getFunctionIdentifier();
          VariableReferenceExpression tempVarExpr = new VariableReferenceExpression(originalProducedVar);
          tempVarExpr.setSourceLocation(agg.getSourceLocation());
          List<Mutable<ILogicalExpression>> arguments = new ArrayList<Mutable<ILogicalExpression>>();
          Mutable<ILogicalExpression> mutableExpression = new MutableObject<ILogicalExpression>(tempVarExpr);
          arguments.add(mutableExpression);
          /**
           * For global aggregate, the merge function is ALWAYS the same as the original aggregate function.
           */
          FunctionIdentifier mergeFid = BuiltinFunctions.isGlobalAggregateFunction(fid) ? fid
                  : BuiltinFunctions.getIntermediateAggregateFunction(fid);
          if (mergeFid == null) {
              /**
               * In this case, no merge function (unimplemented) for the local-side aggregate function
               */
              return null;
          }
          AggregateFunctionCallExpression mergeExpr =
                  BuiltinFunctions.makeAggregateFunctionExpression(mergeFid, arguments);
          mergeExpr.setSourceLocation(agg.getSourceLocation());
          return mergeExpr;
      }
  }
  