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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/pipeline/accumulation_statement.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/value.h"
#include "mongo/util/summation.h"
namespace mongo {
using boost::intrusive_ptr;
REGISTER_ACCUMULATOR(sum, AccumulatorSum::create);
REGISTER_EXPRESSION(sum, ExpressionFromAccumulator<AccumulatorSum>::parse);
const char* AccumulatorSum::getOpName() const {
return "$sum";
}
namespace {
const char subTotalName[] = "subTotal";
const char subTotalErrorName[] = "subTotalError"; // Used for extra precision.
} // namespace
void AccumulatorSum::processInternal(const Value& input, bool merging) {
if (!input.numeric()) {
if (merging && input.getType() == Object) {
// Process merge document, see getValue() below.
nonDecimalTotal.addDouble(
input[subTotalName].getDouble()); // Sum without adjusting type.
processInternal(input[subTotalErrorName], false); // Sum adjusting for type of error.
}
return;
}
// Upgrade to the widest type required to hold the result.
totalType = Value::getWidestNumeric(totalType, input.getType());
switch (input.getType()) {
case NumberInt:
case NumberLong:
nonDecimalTotal.addLong(input.coerceToLong());
break;
case NumberDouble:
nonDecimalTotal.addDouble(input.getDouble());
break;
case NumberDecimal:
decimalTotal = decimalTotal.add(input.coerceToDecimal());
break;
default:
MONGO_UNREACHABLE;
}
}
intrusive_ptr<Accumulator> AccumulatorSum::create(
const boost::intrusive_ptr<ExpressionContext>& expCtx) {
return new AccumulatorSum(expCtx);
}
Value AccumulatorSum::getValue(bool toBeMerged) {
switch (totalType) {
case NumberInt:
if (nonDecimalTotal.fitsLong())
return Value::createIntOrLong(nonDecimalTotal.getLong());
// Fallthrough.
case NumberLong:
if (nonDecimalTotal.fitsLong())
return Value(nonDecimalTotal.getLong());
if (toBeMerged) {
// The value was too large for a NumberLong, so output a document with two values
// adding up to the desired total. Older MongoDB versions used to ignore signed
// integer overflow and cause undefined behavior, that in practice resulted in
// values that would wrap around modulo 2**64. Now an older mongos with a newer
// mongod will yield an error that $sum resulted in a non-numeric type, which is
// OK for this case. Output the error using the totalType, so in the future we can
// determine the correct totalType for the sum. For the error to exceed 2**63,
// more than 2**53 integers would have to be summed, which is impossible.
double total;
double error;
std::tie(total, error) = nonDecimalTotal.getDoubleDouble();
long long llerror = static_cast<long long>(error);
return Value(DOC(subTotalName << total << subTotalErrorName << llerror));
}
// Sum doesn't fit a NumberLong, so return a NumberDouble instead.
return Value(nonDecimalTotal.getDouble());
case NumberDouble:
return Value(nonDecimalTotal.getDouble());
case NumberDecimal: {
double sum, error;
std::tie(sum, error) = nonDecimalTotal.getDoubleDouble();
Decimal128 total; // zero
if (sum != 0) {
total = total.add(Decimal128(sum, Decimal128::kRoundTo34Digits));
total = total.add(Decimal128(error, Decimal128::kRoundTo34Digits));
}
total = total.add(decimalTotal);
return Value(total);
}
default:
MONGO_UNREACHABLE;
}
}
AccumulatorSum::AccumulatorSum(const boost::intrusive_ptr<ExpressionContext>& expCtx)
: Accumulator(expCtx) {
// This is a fixed size Accumulator so we never need to update this.
_memUsageBytes = sizeof(*this);
}
void AccumulatorSum::reset() {
totalType = NumberInt;
nonDecimalTotal = {};
decimalTotal = {};
}
} // namespace mongo
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