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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 "db/dbformat.h"
#include "rocksdb/types.h"
namespace ROCKSDB_NAMESPACE {
class ReadCallback {
public:
explicit ReadCallback(SequenceNumber last_visible_seq)
: max_visible_seq_(last_visible_seq) {}
ReadCallback(SequenceNumber last_visible_seq, SequenceNumber min_uncommitted)
: max_visible_seq_(last_visible_seq), min_uncommitted_(min_uncommitted) {}
virtual ~ReadCallback() {}
// Will be called to see if the seq number visible; if not it moves on to
// the next seq number.
virtual bool IsVisibleFullCheck(SequenceNumber seq) = 0;
inline bool IsVisible(SequenceNumber seq) {
assert(min_uncommitted_ > 0);
assert(min_uncommitted_ >= kMinUnCommittedSeq);
if (seq < min_uncommitted_) { // handles seq == 0 as well
assert(seq <= max_visible_seq_);
return true;
} else if (max_visible_seq_ < seq) {
assert(seq != 0);
return false;
} else {
assert(seq != 0); // already handled in the first if-then clause
return IsVisibleFullCheck(seq);
}
}
inline SequenceNumber max_visible_seq() { return max_visible_seq_; }
// Refresh to a more recent visible seq
virtual void Refresh(SequenceNumber seq) { max_visible_seq_ = seq; }
protected:
// The max visible seq, it is usually the snapshot but could be larger if
// transaction has its own writes written to db.
SequenceNumber max_visible_seq_ = kMaxSequenceNumber;
// Any seq less than min_uncommitted_ is committed.
const SequenceNumber min_uncommitted_ = kMinUnCommittedSeq;
};
} // namespace ROCKSDB_NAMESPACE
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