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.cassandra.index.transactions;
  
  /**
   * Base interface for the handling of index updates.
   * There are 3 types of transaction where indexes are updated to stay in sync with the base table, each represented by
   * a subinterface:
   * * {@code UpdateTransaction}
   *   Used on the regular write path and when indexing newly acquired SSTables from streaming or sideloading. This type
   *   of transaction may include both row inserts and updates to rows previously existing in the base Memtable. Instances
   *   are scoped to a single partition update and are obtained from the factory method
   *   {@code SecondaryIndexManager#newUpdateTransaction}
   *
   * * {@code CompactionTransaction}
   *   Used during compaction when stale entries which have been superceded are cleaned up from the index. As rows in a
   *   partition are merged during the compaction, index entries for any purged rows are cleaned from the index to
   *   compensate for the fact that they may not have been removed at write time if the data in the base table had been
   *   already flushed to disk (and so was processed as an insert, not an update by the UpdateTransaction). These
   *   transactions are currently scoped to a single row within a partition, but this could be improved to batch process
   *   multiple rows within a single partition.
   *
   * * @{code CleanupTransaction}
   *   During cleanup no merging is required, the only thing to do is to notify indexes of the partitions being removed,
   *   along with the rows within those partitions. Like with compaction, these transactions are currently scoped to a
   *   single row within a partition, but this could be improved with batching.
   */
  public interface IndexTransaction
  {
      /**
       * Used to differentiate between type of index transaction when obtaining
       * a handler from Index implementations.
       */
      public enum Type
      {
          UPDATE, COMPACTION, CLEANUP
      }
  
      void start();
      void commit();
  }
  