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/**
* Copyright (C) 2021-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 <functional>
#include "mongo/db/update/update_executor.h"
namespace mongo {
/**
* An UpdateExecutor representing a transform-style update.
*
* A transform-style update is similar to a replacement-style update with the difference that the
* replacement document is calculated from the original document via a user-provided function. In
* case of a WriteConflict or similar where the update needs to be retried the output document will
* be re-calculated.
*
* The replacement function MUST preserve the _id element from the original document.
*
* If the replacement function returns boost::none the update operation will be considered a no-op.
*/
class ObjectTransformExecutor : public UpdateExecutor {
public:
using TransformFunc = std::function<boost::optional<BSONObj>(const BSONObj&)>;
/**
* Applies a transform style update to 'applyParams.element'.
*
* The transform function MUST preserve the _id element in the original document.
*
* This function will ignore the log mode provided in 'applyParams'. The 'oplogEntry' field
* of the returned ApplyResult is always empty.
*/
static ApplyResult applyTransformUpdate(ApplyParams applyParams,
const TransformFunc& transformFunc);
/**
* Initializes the node with the transform function to apply to the original document.
*/
explicit ObjectTransformExecutor(TransformFunc transform);
/**
* Replaces the document that 'applyParams.element' belongs to with result of transform
* function. 'applyParams.element' must be the root of the document. Always returns a result
* stating that indexes are affected when the replacement is not a noop.
*/
ApplyResult applyUpdate(ApplyParams applyParams) const final;
Value serialize() const final;
private:
TransformFunc _transformFunc;
};
} // namespace mongo
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