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;
  
  /**
   * A base class for select aggregate function implementation.&nbsp; Subclasses should provide the
     implementation for aggregate compute functions.
   * <p>
   * <br>
   * <b>Properties : </b> <br>
   * <b>column : </b> Column name for aggregation.
   * <b>alias : </b> Output value alias name.
   * @displayName Function Index
   * @category Stream Manipulators
   * @tags sql aggregate
   * @since 0.3.4
   * @deprecated
   */
  @Deprecated
  public abstract class FunctionIndex
  {
    /**
     * Column name.
     */
    @NotNull
    protected String column;
  
    /**
     * Alias name.
     */
    protected String alias;
  
    /**
     * @param column Column name for aggregation.
     * @param alias Output value alias name.
     */
    public FunctionIndex(@NotNull String column, String alias)
    {
      this.column = column;
      this.alias = alias;
    }
  
    /**
     * Aggregate compute function, implementation in sub class.
     * @param rows Tuple list over application window.
     * @return aggregate result object.
     */
    public abstract Object compute(@NotNull ArrayList<Map<String, Object>> rows) throws Exception;
  
    /**
     * Get aggregate output value name.
     * @return name string.
     */
    protected abstract String aggregateName();
  
    /**
     * Apply compute function to given rows and store result in collect by output value name.
     * @param  rows Tuple list over application window.
     */
    public void filter(ArrayList<Map<String, Object>> rows, Map<String, Object> collect) throws Exception
    {
      if (rows == null) {
        return;
      }
      String name = column;
      if (alias != null) {
        name = alias;
      }
      if (name == null) {
        name = aggregateName();
      }
      collect.put(name, compute(rows));
    }
  }
  