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/**
* Copyright (C) 2017 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/update/update_leaf_node.h"
#include "mongo/stdx/memory.h"
namespace mongo {
/**
* Represents a placeholder update that generates conflicts with other updates on the same path but
* has no effect of its own (i.e., its apply() function does nothing).
*
* We use the ConflictPlaceholderNode to ensure that the "from" path of a $rename does not conflict
* with any other updates. A {$rename: {'from': 'to'}} results in a ConflictPlaceholderNode on the
* "from" path and a RenameNode on the "to" path. The actual rename operation executes with
* RenameNode::apply().
*/
class ConflictPlaceholderNode : public UpdateLeafNode {
public:
Status init(BSONElement modExpr, const boost::intrusive_ptr<ExpressionContext>& expCtx) final {
return Status::OK();
}
std::unique_ptr<UpdateNode> clone() const final {
return stdx::make_unique<ConflictPlaceholderNode>(*this);
}
void setCollator(const CollatorInterface* collator) final {}
ApplyResult apply(ApplyParams applyParams) const final {
return ApplyResult::noopResult();
}
};
} // namespace mongo
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