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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 "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/window_function/partition_iterator.h"
#include "mongo/db/pipeline/window_function/window_bounds.h"
#include "mongo/db/pipeline/window_function/window_function_exec.h"
namespace mongo {
/**
* An executor that specifically handles document-based window types which accumulate values while
* removing old ones.
*/
class WindowFunctionExecRemovableDocument final : public WindowFunctionExecRemovable {
public:
/**
* Constructs a removable window function executor with the given input expression to be
* evaluated and passed to the corresponding WindowFunc for each document in the window.
*
* The 'bounds' parameter is the user supplied bounds for the window.
*/
WindowFunctionExecRemovableDocument(PartitionIterator* iter,
boost::intrusive_ptr<Expression> input,
std::unique_ptr<WindowFunctionState> function,
WindowBounds::DocumentBased bounds);
/**
* Constructs a removable window function executor with the given input expression and sortBy
* expression to be evaluated and passed the evaluation of both "input" and "sortBy" as a single
* input Value of a 2-sized vector (Value{sortByValue, inputValue}) to the corresponding
* WindowFunc for each document in the window.
*
* The "bounds" parameter is the user supplied bounds for the window.
*/
WindowFunctionExecRemovableDocument(PartitionIterator* iter,
boost::intrusive_ptr<Expression> input,
boost::intrusive_ptr<Expression> sortBy,
std::unique_ptr<WindowFunctionState> function,
WindowBounds::DocumentBased bounds)
: WindowFunctionExecRemovableDocument(iter, std::move(input), std::move(function), bounds) {
_sortBy = std::move(sortBy);
_memUsageBytes = sizeof(*this);
}
void reset() final {
_function->reset();
_values = std::queue<Value>();
_initialized = false;
_memUsageBytes = sizeof(*this);
}
private:
void update() final;
void initialize();
void removeFirstValueIfExists() {
if (_values.size() == 0) {
return;
}
_memUsageBytes -= _values.front().getApproximateSize();
_function->remove(_values.front());
_values.pop();
}
// In one of two states: either the initial window has not been populated or we are sliding and
// accumulating/removing values.
bool _initialized = false;
boost::intrusive_ptr<Expression> _sortBy = nullptr;
int _lowerBound;
// Will stay boost::none if right unbounded.
boost::optional<int> _upperBound = boost::none;
};
} // namespace mongo
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