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.
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  package org.apache.asterix.optimizer.rules;
  
  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.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.LogicalVariable;
  import org.apache.hyracks.algebricks.core.algebra.expressions.ScalarFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
  import org.apache.hyracks.algebricks.core.algebra.functions.AlgebricksBuiltinFunctions;
  import org.apache.hyracks.algebricks.core.algebra.functions.IFunctionInfo;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.SelectOperator;
  import org.apache.hyracks.algebricks.rewriter.rules.AbstractIntroduceGroupByCombinerRule;
  import org.apache.hyracks.api.exceptions.SourceLocation;
  
  public class AsterixIntroduceGroupByCombinerRule extends AbstractIntroduceGroupByCombinerRule {
  
      @SuppressWarnings("unchecked")
      @Override
      protected void processNullTest(IOptimizationContext context, GroupByOperator nestedGby,
              List<LogicalVariable> aggregateVarsProducedByCombiner) {
          SourceLocation sourceLoc = nestedGby.getSourceLocation();
          IFunctionInfo finfoEq = context.getMetadataProvider().lookupFunction(BuiltinFunctions.IS_SYSTEM_NULL);
          SelectOperator selectNonSystemNull;
  
          if (aggregateVarsProducedByCombiner.size() == 1) {
              VariableReferenceExpression aggVarRef =
                      new VariableReferenceExpression(aggregateVarsProducedByCombiner.get(0));
              aggVarRef.setSourceLocation(sourceLoc);
              ScalarFunctionCallExpression isSystemNullTest =
                      new ScalarFunctionCallExpression(finfoEq, new MutableObject<>(aggVarRef));
              isSystemNullTest.setSourceLocation(sourceLoc);
              IFunctionInfo finfoNot = context.getMetadataProvider().lookupFunction(AlgebricksBuiltinFunctions.NOT);
              ScalarFunctionCallExpression nonSystemNullTest =
                      new ScalarFunctionCallExpression(finfoNot, new MutableObject<>(isSystemNullTest));
              nonSystemNullTest.setSourceLocation(sourceLoc);
              selectNonSystemNull = new SelectOperator(new MutableObject<>(nonSystemNullTest));
              selectNonSystemNull.setSourceLocation(sourceLoc);
          } else {
              List<Mutable<ILogicalExpression>> isSystemNullTestList = new ArrayList<>();
              for (LogicalVariable aggVar : aggregateVarsProducedByCombiner) {
                  VariableReferenceExpression aggVarRef = new VariableReferenceExpression(aggVar);
                  aggVarRef.setSourceLocation(sourceLoc);
                  ScalarFunctionCallExpression isSystemNullTest =
                          new ScalarFunctionCallExpression(finfoEq, new MutableObject<>(aggVarRef));
                  isSystemNullTest.setSourceLocation(sourceLoc);
                  IFunctionInfo finfoNot = context.getMetadataProvider().lookupFunction(AlgebricksBuiltinFunctions.NOT);
                  ScalarFunctionCallExpression nonSystemNullTest =
                          new ScalarFunctionCallExpression(finfoNot, new MutableObject<>(isSystemNullTest));
                  nonSystemNullTest.setSourceLocation(sourceLoc);
                  isSystemNullTestList.add(new MutableObject<>(nonSystemNullTest));
              }
              IFunctionInfo finfoAnd = context.getMetadataProvider().lookupFunction(AlgebricksBuiltinFunctions.AND);
              selectNonSystemNull = new SelectOperator(
                      new MutableObject<>(new ScalarFunctionCallExpression(finfoAnd, isSystemNullTestList)));
              selectNonSystemNull.setSourceLocation(sourceLoc);
          }
  
          //add the not-system-null check into the nested pipeline
          Mutable<ILogicalOperator> ntsBeforeNestedGby = nestedGby.getInputs().get(0);
          nestedGby.getInputs().set(0, new MutableObject<>(selectNonSystemNull));
          selectNonSystemNull.getInputs().add(ntsBeforeNestedGby);
      }
  }
  