text: /**
   *    Copyright (C) 2018 MongoDB Inc.
   *
   *    This program is free software: you can redistribute it and/or  modify
   *    it under the terms of the GNU Affero General Public License, version 3,
   *    as published by the Free Software Foundation.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    GNU Affero General Public License for more details.
   *
   *    You should have received a copy of the GNU Affero General Public License
   *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
   *
   *    As a special exception, the copyright holders give permission to link the
   *    code of portions of this program with the OpenSSL library under certain
   *    conditions as described in each individual source file and distribute
   *    linked combinations including the program with the OpenSSL library. You
   *    must comply with the GNU Affero General Public License in all respects for
   *    all of the code used other than as permitted herein. If you modify file(s)
   *    with this exception, you may extend this exception to your version of the
   *    file(s), but you are not obligated to do so. If you do not wish to do so,
   *    delete this exception statement from your version. If you delete this
   *    exception statement from all source files in the program, then also delete
   *    it in the license file.
   */
  
  #pragma once
  
  #include <string>
  
  #include "mongo/db/index/multikey_paths.h"
  #include "mongo/db/operation_context.h"
  
  namespace mongo {
  
  struct MultikeyPathInfo {
      NamespaceString nss;
      std::string indexName;
      MultikeyPaths multikeyPaths;
  };
  
  /**
   * An OperationContext decoration that tracks which indexes should be made multikey. This is used
   * by IndexCatalogEntryImpl::setMultikey() to track what indexes should be set as multikey during
   * secondary oplog application. This both marks if the multikey path information should be tracked
   * instead of set immediately and saves the multikey path information for later if needed.
   */
  class MultikeyPathTracker {
  public:
      static const OperationContext::Decoration<MultikeyPathTracker> get;
  
      // Decoration requires a default constructor.
      MultikeyPathTracker() = default;
  
      /**
       * Appends the provided multikey path information to the list of indexes to set as multikey
       * after the current replication batch finishes.
       * Must call startTrackingMultikeyPathInfo() first.
       */
      void addMultikeyPathInfo(MultikeyPathInfo info);
  
      /**
       * Returns the multikey path information that has been saved.
       */
      const std::vector<MultikeyPathInfo>& getMultikeyPathInfo() const;
  
      /**
       * Specifies that we should track multikey path information on this MultikeyPathTracker. This is
       * only expected to be called during oplog application on secondaries. We cannot simply check
       * 'canAcceptWritesFor' because background index builds use their own OperationContext and
       * cannot store their multikey path info here.
       */
      void startTrackingMultikeyPathInfo();
  
      /**
       * Specifies to stop tracking multikey path information.
       */
      void stopTrackingMultikeyPathInfo();
  
      /**
       * Returns if we've called startTrackingMultikeyPathInfo() and not yet called
       * stopTrackingMultikeyPathInfo().
       */
      bool isTrackingMultikeyPathInfo() const;
  
  
  private:
      std::vector<MultikeyPathInfo> _multikeyPathInfo;
      bool _trackMultikeyPathInfo = false;
  };
  
  }  // namespace mongo
  