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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/accumulator_multi.h"
#include "mongo/db/pipeline/window_function/window_function.h"
namespace mongo {
/**
* Adaptor/wrapper class makes AccumulatorTopBottomN fulfill the interface of a window function.
* This is possible since this particular accumulator has a remove() method.
*/
template <TopBottomSense sense, bool single>
class WindowFunctionTopBottomN : public WindowFunctionState {
public:
static std::unique_ptr<WindowFunctionState> create(ExpressionContext* const expCtx,
SortPattern sp,
long long n) {
return std::make_unique<WindowFunctionTopBottomN<sense, single>>(expCtx, std::move(sp), n);
}
static AccumulationExpression parse(ExpressionContext* const expCtx,
BSONElement elem,
VariablesParseState vps) {
return AccumulatorTopBottomN<sense, single>::parseTopBottomN(expCtx, elem, vps);
}
explicit WindowFunctionTopBottomN(ExpressionContext* const expCtx, SortPattern sp, long long n)
: WindowFunctionState(expCtx), _acc(expCtx, std::move(sp), true) {
_acc.startNewGroup(Value(n));
_memUsageBytes = sizeof(*this);
}
void add(Value value) final {
_acc.process(value, false);
_memUsageBytes = _acc.getMemUsage();
}
void remove(Value value) final {
_acc.remove(value);
_memUsageBytes = _acc.getMemUsage();
}
Value getValue() const final {
return _acc.getValueConst(false);
}
void reset() final {
_acc.reset();
_memUsageBytes = _acc.getMemUsage();
}
private:
AccumulatorTopBottomN<sense, single> _acc;
};
using WindowFunctionTopN = WindowFunctionTopBottomN<TopBottomSense::kTop, false>;
using WindowFunctionBottomN = WindowFunctionTopBottomN<TopBottomSense::kBottom, false>;
using WindowFunctionTop = WindowFunctionTopBottomN<TopBottomSense::kTop, true>;
using WindowFunctionBottom = WindowFunctionTopBottomN<TopBottomSense::kBottom, true>;
}; // namespace mongo
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