ceph/src/rocksdb/db/snapshot_checker.h

   1 // Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5
   6 #pragma once
   7 #include "rocksdb/types.h"
   8
   9 namespace rocksdb {
  10
  11 enum class SnapshotCheckerResult : int {
  12   kInSnapshot = 0,
  13   kNotInSnapshot = 1,
  14   // In case snapshot is released and the checker has no clue whether
  15   // the given sequence is visible to the snapshot.
  16   kSnapshotReleased = 2,
  17 };
  18
  19 // Callback class that control GC of duplicate keys in flush/compaction.
  20 class SnapshotChecker {
  21  public:
  22   virtual ~SnapshotChecker() {}
  23   virtual SnapshotCheckerResult CheckInSnapshot(
  24       SequenceNumber sequence, SequenceNumber snapshot_sequence) const = 0;
  25 };
  26
  27 class DisableGCSnapshotChecker : public SnapshotChecker {
  28  public:
  29   virtual ~DisableGCSnapshotChecker() {}
  30   virtual SnapshotCheckerResult CheckInSnapshot(
  31       SequenceNumber /*sequence*/,
  32       SequenceNumber /*snapshot_sequence*/) const override {
  33     // By returning kNotInSnapshot, we prevent all the values from being GCed
  34     return SnapshotCheckerResult::kNotInSnapshot;
  35   }
  36   static DisableGCSnapshotChecker* Instance() { return &instance_; }
  37
  38  protected:
  39   static DisableGCSnapshotChecker instance_;
  40   explicit DisableGCSnapshotChecker() {}
  41 };
  42
  43 class WritePreparedTxnDB;
  44
  45 // Callback class created by WritePreparedTxnDB to check if a key
  46 // is visible by a snapshot.
  47 class WritePreparedSnapshotChecker : public SnapshotChecker {
  48  public:
  49   explicit WritePreparedSnapshotChecker(WritePreparedTxnDB* txn_db);
  50   virtual ~WritePreparedSnapshotChecker() {}
  51
  52   virtual SnapshotCheckerResult CheckInSnapshot(
  53       SequenceNumber sequence, SequenceNumber snapshot_sequence) const override;
  54
  55  private:
  56 #ifndef ROCKSDB_LITE
  57   const WritePreparedTxnDB* const txn_db_;
  58 #endif  // !ROCKSDB_LITE
  59 };
  60
  61 }  // namespace rocksdb