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 org.apache.asterix.runtime.aggregates.base.SingleFieldFrameTupleReference;
  import org.apache.hyracks.algebricks.runtime.base.IAggregateEvaluator;
  import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
  import org.apache.hyracks.algebricks.runtime.base.IUnnestingEvaluator;
  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.IPointable;
  import org.apache.hyracks.data.std.primitive.VoidPointable;
  import org.apache.hyracks.dataflow.common.data.accessors.IFrameTupleReference;
  
  /**
   * Implements scalar aggregates by iterating over a collection with the ScanCollection unnesting function,
   * and applying the corresponding aggregate function to each collection-item.
   */
  public class GenericScalarAggregateFunction implements IScalarEvaluator {
  
      private final IAggregateEvaluator aggFunc;
  
      private final IUnnestingEvaluator scanCollection;
  
      private final IPointable listItemOut = new VoidPointable();
  
      private final SingleFieldFrameTupleReference itemTuple = new SingleFieldFrameTupleReference();
  
      protected final SourceLocation sourceLoc;
  
      public GenericScalarAggregateFunction(IAggregateEvaluator aggFunc, IUnnestingEvaluatorFactory scanCollectionFactory,
              IEvaluatorContext context, SourceLocation sourceLoc) throws HyracksDataException {
          this.aggFunc = aggFunc;
          this.scanCollection = scanCollectionFactory.createUnnestingEvaluator(context);
          this.sourceLoc = sourceLoc;
      }
  
      @Override
      public void evaluate(IFrameTupleReference tuple, IPointable result) throws HyracksDataException {
          scanCollection.init(tuple);
          aggInit();
          while (scanCollection.step(listItemOut)) {
              aggStep(listItemOut);
          }
          aggFinish(result);
      }
  
      protected void aggInit() throws HyracksDataException {
          aggFunc.init();
      }
  
      protected void aggStep(IPointable item) throws HyracksDataException {
          itemTuple.reset(item.getByteArray(), item.getStartOffset(), item.getLength());
          aggFunc.step(itemTuple);
      }
  
      protected void aggFinish(IPointable result) throws HyracksDataException {
          aggFunc.finish(result);
      }
  }
  