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.apex.malhar.contrib.misc.streamquery.function;
  
  import java.util.ArrayList;
  import java.util.Map;
  
  import javax.validation.constraints.NotNull;
  
  import org.apache.commons.lang.StringUtils;
  
  /**
   * An implementation of function index that implements average function semantics. <br>
   * <p>
   *   e.g : sql => SELECT AVG(column_name) FROM table_name. <br>
   *   <br>
   *   <b> Properties : </b> <br>
   *   <b> column : </b> Aggregate over given column values.   <br>
   *   <b> alias  : </b> Alias name for aggregate output. <br>
   * @displayName Average Function
   * @category Stream Manipulators
   * @tags sql average
   * @since 0.3.4
   * @deprecated
   */
  @Deprecated
  public class AverageFunction extends FunctionIndex
  {
    /**
     * @param column Aggregate over given column values, must be non null.
     * @param alias  Alias name for aggregate output.
     */
    public AverageFunction(@NotNull String column, String alias)
    {
      super(column, alias);
    }
  
    /**
     * Compute average for given column values.
     */
    @Override
    public Object compute(@NotNull ArrayList<Map<String, Object>> rows) throws Exception
    {
      if (rows.size() == 0) {
        return 0.0;
      }
      double sum = 0.0;
      for (Map<String, Object> row : rows) {
        sum += ((Number)row.get(column)).doubleValue();
      }
      return sum / rows.size();
    }
  
    /**
     * Get aggregate name.
     * @return name.
     */
    @Override
    protected String aggregateName()
    {
      if (!StringUtils.isEmpty(alias)) {
        return alias;
      }
      return "AVG(" + column + ")";
    }
  }
  