rocksdb/db/snapshot_checker.h

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// 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 {
// Callback class that control GC of duplicate keys in flush/compaction
class SnapshotChecker {
public:
virtual ~SnapshotChecker() {}
virtual bool IsInSnapshot(SequenceNumber sequence,
SequenceNumber snapshot_sequence) const = 0;
};
class DisableGCSnapshotChecker : public SnapshotChecker {
public:
virtual ~DisableGCSnapshotChecker() {}
virtual bool IsInSnapshot(
SequenceNumber /*sequence*/,
SequenceNumber /*snapshot_sequence*/) const override {
// By returning false, we prevent all the values from being GCed
return false;
}
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 bool IsInSnapshot(SequenceNumber sequence,
SequenceNumber snapshot_sequence) const override;
private:
#ifndef ROCKSDB_LITE
const WritePreparedTxnDB* const txn_db_;
#endif // !ROCKSDB_LITE
};
} // namespace rocksdb