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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.
*/
#include "mongo/platform/basic.h"
#include <cmath>
#include <limits>
#include "mongo/db/pipeline/accumulator.h"
#include "mongo/db/exec/document_value/value.h"
#include "mongo/db/pipeline/accumulation_statement.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/window_function/window_function_expression.h"
namespace mongo {
using boost::intrusive_ptr;
REGISTER_STABLE_WINDOW_FUNCTION(expMovingAvg,
mongo::window_function::ExpressionExpMovingAvg::parse);
void AccumulatorExpMovingAvg::processInternal(const Value& input, bool merging) {
tassert(5433600, "$expMovingAvg can't be merged", !merging);
if (!input.numeric()) {
return;
}
if (input.getType() == BSONType::NumberDecimal) {
_isDecimal = true;
}
auto decimalVal = input.coerceToDecimal();
if (!_init) {
_currentResult = decimalVal;
_init = true;
} else {
_currentResult = decimalVal.multiply(_alpha).add(
_currentResult.multiply(Decimal128(1).subtract(_alpha)));
}
}
intrusive_ptr<AccumulatorState> AccumulatorExpMovingAvg::create(ExpressionContext* const expCtx,
Decimal128 alpha) {
return new AccumulatorExpMovingAvg(expCtx, alpha);
}
Value AccumulatorExpMovingAvg::getValue(bool toBeMerged) {
tassert(5433601, "$expMovingAvg can't be merged", !toBeMerged);
if (!_init) {
return Value(BSONNULL);
}
if (!_isDecimal) {
return Value(_currentResult.toDouble());
}
return Value(_currentResult);
}
AccumulatorExpMovingAvg::AccumulatorExpMovingAvg(ExpressionContext* const expCtx, Decimal128 alpha)
: AccumulatorState(expCtx), _alpha(alpha) {
_memUsageBytes = sizeof(*this);
}
void AccumulatorExpMovingAvg::reset() {
_memUsageBytes = sizeof(*this);
_init = false;
}
} // namespace mongo
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