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.runtime.aggregates.scalar;
  
  import java.util.List;
  
  import org.apache.asterix.builders.AbvsBuilderFactory;
  import org.apache.asterix.builders.ArrayListFactory;
  import org.apache.asterix.om.types.ATypeTag;
  import org.apache.asterix.om.types.IAType;
  import org.apache.asterix.om.util.container.IObjectPool;
  import org.apache.asterix.om.util.container.ListObjectPool;
  import org.apache.asterix.runtime.aggregates.utils.PointableHashSet;
  import org.apache.hyracks.algebricks.runtime.base.IAggregateEvaluator;
  import org.apache.hyracks.algebricks.runtime.base.IUnnestingEvaluatorFactory;
  import org.apache.hyracks.api.context.IEvaluatorContext;
  import org.apache.hyracks.api.exceptions.HyracksDataException;
  import org.apache.hyracks.api.exceptions.SourceLocation;
  import org.apache.hyracks.data.std.api.IMutableValueStorage;
  import org.apache.hyracks.data.std.api.IPointable;
  import org.apache.hyracks.data.std.util.ArrayBackedValueStorage;
  
  /**
   * Implements scalar distinct aggregates by iterating over a collection with the ScanCollection unnesting function,
   * and applying the corresponding aggregate function to each distinct collection-item.
   */
  public class GenericScalarDistinctAggregateFunction extends GenericScalarAggregateFunction {
  
      private final IObjectPool<IMutableValueStorage, ATypeTag> storageAllocator;
  
      private final IObjectPool<List<IPointable>, ATypeTag> arrayListAllocator;
  
      private final PointableHashSet itemSet;
  
      public GenericScalarDistinctAggregateFunction(IAggregateEvaluator aggFunc,
              IUnnestingEvaluatorFactory scanCollectionFactory, IEvaluatorContext context, SourceLocation sourceLoc,
              IAType itemType) throws HyracksDataException {
          super(aggFunc, scanCollectionFactory, context, sourceLoc);
          storageAllocator = new ListObjectPool<>(new AbvsBuilderFactory());
          arrayListAllocator = new ListObjectPool<>(new ArrayListFactory<>());
          itemSet = new PointableHashSet(arrayListAllocator, itemType) {
              @Override
              protected IPointable makeStoredItem(IPointable item) throws HyracksDataException {
                  ArrayBackedValueStorage abvs = (ArrayBackedValueStorage) storageAllocator.allocate(null);
                  abvs.assign(item);
                  return abvs;
              }
          };
      }
  
      @Override
      protected void aggInit() throws HyracksDataException {
          super.aggInit();
  
          storageAllocator.reset();
          arrayListAllocator.reset();
          itemSet.clear();
      }
  
      @Override
      protected void aggStep(IPointable item) throws HyracksDataException {
          if (itemSet.add(item)) {
              super.aggStep(item);
          }
      }
  }
  