You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
rocksdb/db/read_callback.h

53 lines
1.7 KiB

// 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 {
class ReadCallback {
public:
ReadCallback() {}
ReadCallback(SequenceNumber snapshot) : snapshot_(snapshot) {}
ReadCallback(SequenceNumber snapshot, SequenceNumber min_uncommitted)
: snapshot_(snapshot), 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) {
if (seq == 0 || seq < min_uncommitted_) {
assert(seq <= snapshot_);
return true;
} else if (snapshot_ < seq) {
return false;
} else {
return IsVisibleFullCheck(seq);
}
}
// This is called to determine the maximum visible sequence number for the
// current transaction for read-your-own-write semantics. This is so that
// for write unprepared, we will not skip keys that are written by the
// current transaction with the seek to snapshot optimization.
//
// For other uses, this returns zero, meaning that the current snapshot
// sequence number is the maximum visible sequence number.
inline virtual SequenceNumber MaxUnpreparedSequenceNumber() { return 0; };
protected:
// The snapshot at which the read is performed.
const SequenceNumber snapshot_ = kMaxSequenceNumber;
// Any seq less than min_uncommitted_ is committed.
const SequenceNumber min_uncommitted_ = 0;
};
} // namespace rocksdb