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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.
*/
#include "mongo/db/pipeline/window_function/window_function_integral.h"
#include "mongo/db/pipeline/accumulator.h"
namespace mongo {
Value WindowFunctionIntegral::integralOfTwoPointsByTrapezoidalRule(const Value& preValue,
const Value& newValue) {
auto preArr = preValue.getArray();
auto newArr = newValue.getArray();
if (preArr[0].isNaN() || preArr[1].isNaN() || newArr[0].isNaN() || newArr[1].isNaN())
return Value(0);
if ((preArr[0].getType() == BSONType::Date && newArr[0].getType() == BSONType::Date) ||
(preArr[0].numeric() && newArr[0].numeric())) {
// Now 'newValue' and 'preValue' are either both numeric, or both dates.
// $subtract on two dates gives us the difference in milliseconds.
Value delta = uassertStatusOK(ExpressionSubtract::apply(newArr[0], preArr[0]));
Value sumY = uassertStatusOK(ExpressionAdd::apply(newArr[1], preArr[1]));
Value integral = uassertStatusOK(ExpressionMultiply::apply(sumY, delta));
return uassertStatusOK(ExpressionDivide::apply(integral, Value(2.0)));
} else {
return Value(0);
}
}
void WindowFunctionIntegral::assertValueType(const Value& value) {
tassert(5423900,
"The input value of $integral window function must be a vector of 2 value, the first "
"value must be numeric or date type and the second must be numeric.",
value.isArray() && value.getArray().size() == 2 && value.getArray()[1].numeric() &&
(value.getArray()[0].numeric() || value.getArray()[0].getType() == BSONType::Date));
auto arr = value.getArray();
if (_outputUnitMillis) {
tassert(5423901,
"$integral with 'outputUnit' expects the sortBy field to be a Date",
arr[0].getType() == BSONType::Date);
} else {
tassert(5423902,
"$integral (with no 'outputUnit') expects the sortBy field to be numeric",
arr[0].numeric());
}
}
void WindowFunctionIntegral::add(Value value) {
assertValueType(value);
auto arr = value.getArray();
if (arr[0].isNaN() || arr[1].isNaN())
_nanCount++;
// Update "_integral" if there are at least two values including the value to add.
if (_values.size() > 0) {
_integral.add(integralOfTwoPointsByTrapezoidalRule(_values.back(), value));
}
_memUsageBytes += value.getApproximateSize();
_values.emplace_back(std::move(value));
}
void WindowFunctionIntegral::remove(Value value) {
assertValueType(value);
tassert(5423903, "Can't remove from an empty WindowFunctionIntegral", _values.size() > 0);
tassert(
5423904,
"Attempted to remove an element other than the first element from WindowFunctionIntegral",
_expCtx->getValueComparator().evaluate(_values.front() == value));
auto arr = value.getArray();
if (arr[0].isNaN() || arr[1].isNaN())
_nanCount--;
_memUsageBytes -= value.getApproximateSize();
_values.pop_front();
// Update "_integral" if there are at least two values before removing the current value.
// In the case that the value to remove is the last value in the window, the integral is
// guaranteed to be 0, so there is no need to update '_integral'.
if (_values.size() > 0) {
_integral.remove(integralOfTwoPointsByTrapezoidalRule(value, _values.front()));
}
}
} // namespace mongo
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