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.std;
  
  import org.apache.asterix.om.types.ATypeTag;
  import org.apache.asterix.om.types.IAType;
  import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
  import org.apache.hyracks.api.context.IEvaluatorContext;
  import org.apache.hyracks.api.exceptions.HyracksDataException;
  import org.apache.hyracks.api.exceptions.SourceLocation;
  
  /**
   * SQL min/max functions will mark aggregation as NULL and start to skip aggregating tuples when:
   * <ul>
   *     <li>NULL/MISSING value was encountered globally</li>
   *     <li>Input data type is invalid (i.e. min/max on records) or incompatible (i.e. min/max on string & int)</li>
   * </ul>
   * When NULL/MISSING value is encountered, local aggregator will ignore and continue aggregation. Global aggregator
   * will mark aggregation as NULL since getting NULL/MISSING at the global level indicates type invalidity (Some
   * aggregators are global in nature yet they ignore NULLs similar to a local aggregator, e.g. scalar min/max, normal
   * global aggregators with no local aggregators like distinct min/max (one-step aggregators)).
   */
  public class SqlMinMaxAggregateFunction extends AbstractMinMaxAggregateFunction {
  
      SqlMinMaxAggregateFunction(IScalarEvaluatorFactory[] args, IEvaluatorContext context, boolean isMin, Type type,
              SourceLocation sourceLoc, IAType aggFieldType) throws HyracksDataException {
          super(args, context, isMin, sourceLoc, type, aggFieldType);
      }
  
      @Override
      protected void processNull() {
          if (type == Type.GLOBAL || type == Type.INTERMEDIATE) {
              // getting NULL at the global step should only mean the local step ran into type invalidity
              aggType = ATypeTag.NULL;
          }
      }
  }
  