1 files changed, 61 insertions, 0 deletions
diff --git a/src/rocksdb/db/snapshot_checker.h b/src/rocksdb/db/snapshot_checker.h
new file mode 100644
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+++ b/src/rocksdb/db/snapshot_checker.h
@@ -0,0 +1,61 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+#include "rocksdb/types.h"
+
+namespace rocksdb {
+
+enum class SnapshotCheckerResult : int {
+  kInSnapshot = 0,
+  kNotInSnapshot = 1,
+  // In case snapshot is released and the checker has no clue whether
+  // the given sequence is visible to the snapshot.
+  kSnapshotReleased = 2,
+};
+
+// Callback class that control GC of duplicate keys in flush/compaction.
+class SnapshotChecker {
+ public:
+  virtual ~SnapshotChecker() {}
+  virtual SnapshotCheckerResult CheckInSnapshot(
+      SequenceNumber sequence, SequenceNumber snapshot_sequence) const = 0;
+};
+
+class DisableGCSnapshotChecker : public SnapshotChecker {
+ public:
+  virtual ~DisableGCSnapshotChecker() {}
+  virtual SnapshotCheckerResult CheckInSnapshot(
+      SequenceNumber /*sequence*/,
+      SequenceNumber /*snapshot_sequence*/) const override {
+    // By returning kNotInSnapshot, we prevent all the values from being GCed
+    return SnapshotCheckerResult::kNotInSnapshot;
+  }
+  static DisableGCSnapshotChecker* Instance() { return &instance_; }
+
+ protected:
+  static DisableGCSnapshotChecker instance_;
+  explicit DisableGCSnapshotChecker() {}
+};
+
+class WritePreparedTxnDB;
+
+// Callback class created by WritePreparedTxnDB to check if a key
+// is visible by a snapshot.
+class WritePreparedSnapshotChecker : public SnapshotChecker {
+ public:
+  explicit WritePreparedSnapshotChecker(WritePreparedTxnDB* txn_db);
+  virtual ~WritePreparedSnapshotChecker() {}
+
+  virtual SnapshotCheckerResult CheckInSnapshot(
+      SequenceNumber sequence, SequenceNumber snapshot_sequence) const override;
+
+ private:
+#ifndef ROCKSDB_LITE
+  const WritePreparedTxnDB* const txn_db_;
+#endif  // !ROCKSDB_LITE
+};
+
+}  // namespace rocksdb