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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/db/repl/oplog_entry.h"
namespace mongo {
class OperationContext;
/**
* An iterator class that traverses backwards through a transaction's oplog entries by following the
* "prevOpTime" link in each entry.
*/
class TransactionHistoryIteratorBase {
public:
virtual ~TransactionHistoryIteratorBase() = default;
/**
* Returns false if there are no more entries to iterate.
*/
virtual bool hasNext() const = 0;
/**
* Returns an oplog entry and advances the iterator one step back through the oplog.
* Should not be called if hasNext is false.
* Throws if next oplog entry is in a unrecognized format or if it can't find the next oplog
* entry.
*/
virtual repl::OplogEntry next(OperationContext* opCtx) = 0;
/**
* Same as next() but returns only the OpTime, instead of the entire entry.
*/
virtual repl::OpTime nextOpTime(OperationContext* opCtx) = 0;
};
class TransactionHistoryIterator : public TransactionHistoryIteratorBase {
public:
/**
* Creates a new iterator starting with an oplog entry with the given start opTime.
*/
TransactionHistoryIterator(repl::OpTime startingOpTime, bool permitYield = false);
virtual ~TransactionHistoryIterator() = default;
bool hasNext() const override;
repl::OplogEntry next(OperationContext* opCtx) override;
repl::OpTime nextOpTime(OperationContext* opCtx) override;
/**
* Same as next() but makes exceptions fatal.
*/
repl::OplogEntry nextFatalOnErrors(OperationContext* opCtx);
private:
// Clients can set this to allow PlanExecutors created by this TransactionHistoryIterator to
// have a YIELD_AUTO yield policy. It is only safe to set this if next() will never be called
// while holding a lock that should not be yielded, such as the PBWM lock.
bool _permitYield;
repl::OpTime _nextOpTime;
};
} // namespace mongo
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