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.arrow.algorithm.dictionary;
  
  import org.apache.arrow.vector.ValueVector;
  
  /**
   * A dictionary builder is intended for the scenario frequently encountered in practice: the
   * dictionary is not known a priori, so it is generated dynamically. In particular, when a new value
   * arrives, it is tested to check if it is already in the dictionary. If so, it is simply neglected,
   * otherwise, it is added to the dictionary.
   *
   * <p>The dictionary builder is intended to build a single dictionary. So it cannot be used for
   * different dictionaries.
   *
   * <p>Below gives the sample code for using the dictionary builder
   *
   * <pre>{@code
   * DictionaryBuilder dictionaryBuilder = ...
   * ...
   * dictionaryBuild.addValue(newValue);
   * ...
   * }</pre>
   *
   * <p>With the above code, the dictionary vector will be populated, and it can be retrieved by the
   * {@link DictionaryBuilder#getDictionary()} method. After that, dictionary encoding can proceed
   * with the populated dictionary..
   *
   * @param <V> the dictionary vector type.
   */
  public interface DictionaryBuilder<V extends ValueVector> {
  
    /**
     * Try to add all values from the target vector to the dictionary.
     *
     * @param targetVector the target vector containing values to probe.
     * @return the number of values actually added to the dictionary.
     */
    int addValues(V targetVector);
  
    /**
     * Try to add an element from the target vector to the dictionary.
     *
     * @param targetVector the target vector containing new element.
     * @param targetIndex the index of the new element in the target vector.
     * @return the index of the new element in the dictionary.
     */
    int addValue(V targetVector, int targetIndex);
  
    /**
     * Gets the dictionary built.
     *
     * @return the dictionary.
     */
    V getDictionary();
  }
  