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.carbondata.core.util;
  
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.List;
  import java.util.Map;
  
  /**
   * Abstract class for Custom Index implementation. When index property is configured on table, a
   * new column is created within carbon layer from the set of schema columns in the table.
   * An Index implementation class must extend this class and provide the concrete implementation
   * for following abstract methods:
   * 1. Init method to extract and store the sub-properties of index property. Such as index type,
   *    source columns etc.
   * 2. Generate method to generate the row value for the index column from corresponding row values
   *    of its source columns.
   * 3. Query method to process the custom UDF filter queries based on source columns.
   * @param <ReturnType>
   */
  public abstract class CustomIndex<ReturnType> implements Serializable {
  
    private static final long serialVersionUID = 6529685098267757692L;
    /**
     * Initialize the custom index instance.
     * @param indexName
     * @param properties
     * @throws Exception
     */
    public abstract void init(String indexName, Map<String, String> properties) throws Exception;
  
    /**
     * Generates the custom index column value from the given source columns.
     * @param columns
     * @return Returns generated column value
     * @throws Exception
     */
    public abstract String generate(List<?> columns) throws Exception;
  
    /**
     * Query processor for custom index.
     * @param query
     * @return Returns list of ranges to be fetched
     * @throws Exception
     */
    public abstract ReturnType query(String query) throws Exception;
  
    /**
     * Query processor for custom index.
     * @param queryPointList query point list for GeoHashIndex
     * @return Returns list of ranges to be fetched
     * @throws Exception
     */
    public abstract ReturnType query(List<double[]> queryPointList) throws Exception;
  
    /**
     * Deserializes and returns the custom index instance
     * @param serializedInstance
     * @return
     * @throws IOException
     * @throws ClassNotFoundException
     */
    public static CustomIndex getCustomInstance(String serializedInstance) throws IOException {
      return (CustomIndex) ObjectSerializationUtil.convertStringToObject(serializedInstance);
    }
  
    /**
     * Serializes the custom index instance
     * @param instance
     * @return
     * @throws IOException
     */
    public static String getCustomInstance(CustomIndex instance) throws IOException {
      return ObjectSerializationUtil.convertObjectToString(instance);
    }
  }
  