sapling/eden/fs/rocksdb/RocksHandles.h

/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This software may be used and distributed according to the terms of the
 * GNU General Public License version 2.
 */

#pragma once

#include <folly/String.h>
#include <rocksdb/db.h>
#include <memory>
#include <string>

namespace facebook {
namespace eden {

enum class RocksDBOpenMode {
  ReadOnly,
  ReadWrite,
};

/**
 * This class is the holder of the database and column family handles
 * required to interact with our local rocksdb store.
 * RocksDB requires that we delete the column family handles prior
 * to deleting the DB so we need to manage the lifetime and
 * destruction order with this class.
 */
struct RocksHandles {
  std::unique_ptr<rocksdb::DB> db;

  // The order of these columns matches the descriptors passed
  // as column_descriptors to createRocksDb().
  std::vector<std::unique_ptr<rocksdb::ColumnFamilyHandle>> columns;

  /**
   * Note that the columns MUST be destroyed prior to the DB,
   * so we have a custom destructor for that purpose.
   */
  ~RocksHandles();

  /**
   * Returns an instance of a RocksDB that uses the specified directory for
   * storage. If there is an existing RocksDB at that path with
   * column_descriptors that match the requested set then it will be opened and
   * returned.  If there is no existing RocksDB at that location a new one will
   * be initialized using the requested column_descriptors.  Otherwise (an
   * existing RocksDB has mismatched column_descriptors) will throw an
   * exception.
   */
  RocksHandles(
      folly::StringPiece dbPath,
      RocksDBOpenMode mode,
      const rocksdb::Options& options,
      const std::vector<rocksdb::ColumnFamilyDescriptor>& columnDescriptors);

  RocksHandles(RocksHandles&&) = default;
  RocksHandles& operator=(RocksHandles&&) = default;

  void close();
};
} // namespace eden
} // namespace facebook