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/**
* Copyright (C) 2023-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/accumulation_statement.h"
#include "mongo/db/pipeline/accumulator_percentile_gen.h"
#include "mongo/db/pipeline/percentile_algo.h"
namespace mongo {
/**
* Accumulator for computing $percentile.
*/
class AccumulatorPercentile : public AccumulatorState {
public:
static constexpr auto kName = "$percentile"_sd;
const char* getOpName() const {
return kName.rawData();
}
/**
* Checks that 'pv' is an array of valid percentile specifications. Called by the IDL file.
*/
static Status validatePercentileArg(const std::vector<double>& pv);
/**
* Parsing and creating the accumulator. A separate accumulator object is created per group.
*/
static AccumulationExpression parseArgs(ExpressionContext* expCtx,
BSONElement elem,
VariablesParseState vps);
static boost::intrusive_ptr<Expression> parseExpression(ExpressionContext* expCtx,
BSONElement elem,
VariablesParseState vps);
static boost::intrusive_ptr<AccumulatorState> create(ExpressionContext* expCtx,
const std::vector<double>& ps,
int32_t method);
AccumulatorPercentile(ExpressionContext* expCtx, const std::vector<double>& ps, int32_t method);
/**
* Ingressing values and computing the requested percentiles.
*/
void processInternal(const Value& input, bool merging) final;
Value getValue(bool toBeMerged);
/**
* Other infra for the accumulators.
*/
void reset() final;
/**
* Necessary for supporting $percentile as window functions and/or as expression.
*/
static std::pair<std::vector<double> /*ps*/, int32_t /*method*/> parsePercentileAndMethod(
BSONElement elem);
static Value formatFinalValue(int nPercentiles, const std::vector<double>& pctls);
/**
* Serializes this accumulator to a valid MQL accumulation statement that would be legal
* inside a $group. When executing on a sharded cluster, the result of this function will be
* sent to each individual shard.
*
* The implementation in 'AccumulatorState' assumes the accumulator has the simple syntax {
* <name>: <argument> }, such as { $sum: <argument> }. Because $percentile's syntax is more
* complex ({$percentile: {p: [0.5, 0.8], input: "$x", method: "approximate"}}) we have to
* override this method.
*/
Document serialize(boost::intrusive_ptr<Expression> initializer,
boost::intrusive_ptr<Expression> argument,
SerializationOptions options) const;
/**
* Helper that allows both the accumulator and expression $percentile to serialize their
* corresponding instance variables.
*/
static void serializeHelper(const boost::intrusive_ptr<Expression>& argument,
SerializationOptions options,
std::vector<double> percentiles,
int32_t method,
MutableDocument& md);
protected:
std::vector<double> _percentiles;
std::unique_ptr<PercentileAlgorithm> _algo;
// TODO SERVER-74894: This should have been 'PercentileMethodEnum' but the generated
// header from the IDL includes this header, creating a dependency.
const int32_t _method;
};
/*
* Accumulator for computing $median. $median has the same semantics as $percentile with the 'p'
* field set to [0.5].
*/
class AccumulatorMedian : public AccumulatorPercentile {
public:
static constexpr auto kName = "$median"_sd;
const char* getOpName() const final {
return kName.rawData();
}
/**
* Parsing and creating the accumulator.
*/
static AccumulationExpression parseArgs(ExpressionContext* expCtx,
BSONElement elem,
VariablesParseState vps);
static boost::intrusive_ptr<Expression> parseExpression(ExpressionContext* expCtx,
BSONElement elem,
VariablesParseState vps);
static boost::intrusive_ptr<AccumulatorState> create(ExpressionContext* expCtx,
const std::vector<double>& unused,
int32_t method);
/**
* We are matching the signature of the AccumulatorPercentile for the purpose of using
* ExpressionFromAccumulatorQuantile as a template for both $median and $percentile. This is the
* reason for passing in `unused` and it will not be referenced.
*/
AccumulatorMedian(ExpressionContext* expCtx, const std::vector<double>& unused, int32_t method);
/**
* Necessary for supporting $median as window functions and/or as expression.
*/
static std::pair<std::vector<double> /*ps*/, int32_t /*method*/> parsePercentileAndMethod(
BSONElement elem);
static Value formatFinalValue(int nPercentiles, const std::vector<double>& pctls);
/**
* Modify the base-class implementation to return a single value rather than a single-element
* array.
*/
Value getValue(bool toBeMerged) final;
Document serialize(boost::intrusive_ptr<Expression> initializer,
boost::intrusive_ptr<Expression> argument,
SerializationOptions options) const;
/**
* Helper that allows both the accumulator and expression $median to serialize their
* corresponding instance variables.
*/
static void serializeHelper(const boost::intrusive_ptr<Expression>& argument,
SerializationOptions options,
std::vector<double> percentiles,
int32_t method,
MutableDocument& md);
};
} // namespace mongo
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