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/**
* Copyright (C) 2019-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 <boost/intrusive_ptr.hpp>
#include <vector>
#include "mongo/db/pipeline/accumulation_statement.h"
#include "mongo/db/pipeline/accumulator.h"
#include "mongo/db/pipeline/expression_context.h"
namespace mongo {
class AccumulatorInternalJsReduce final : public AccumulatorState {
public:
static constexpr auto kAccumulatorName = "$_internalJsReduce"_sd;
static boost::intrusive_ptr<AccumulatorState> create(ExpressionContext* const expCtx,
StringData funcSource);
static AccumulationExpression parseInternalJsReduce(ExpressionContext* const expCtx,
BSONElement elem,
VariablesParseState vps);
AccumulatorInternalJsReduce(ExpressionContext* const expCtx, StringData funcSource)
: AccumulatorState(expCtx), _funcSource(funcSource) {
_memUsageBytes = sizeof(*this);
}
const char* getOpName() const final {
return kAccumulatorName.rawData();
}
void processInternal(const Value& input, bool merging) final;
Value getValue(bool toBeMerged) final;
void reset() final;
virtual Document serialize(boost::intrusive_ptr<Expression> initializer,
boost::intrusive_ptr<Expression> argument,
bool explain) const override;
private:
static std::string parseReduceFunction(BSONElement func);
std::string _funcSource;
std::vector<Value> _values;
Value _key;
};
class AccumulatorJs final : public AccumulatorState {
public:
static constexpr auto kAccumulatorName = "$accumulator"_sd;
const char* getOpName() const final {
return kAccumulatorName.rawData();
}
// An AccumulatorState instance only owns its "static" arguments: those that don't need to be
// evaluated per input document.
static boost::intrusive_ptr<AccumulatorState> create(ExpressionContext* const expCtx,
std::string init,
std::string accumulate,
std::string merge,
boost::optional<std::string> finalize);
static AccumulationExpression parse(ExpressionContext* const expCtx,
BSONElement elem,
VariablesParseState vps);
Value getValue(bool toBeMerged) final;
void reset() final;
void processInternal(const Value& input, bool merging) final;
Document serialize(boost::intrusive_ptr<Expression> initializer,
boost::intrusive_ptr<Expression> argument,
bool explain) const final;
void startNewGroup(Value const& input) final;
private:
AccumulatorJs(ExpressionContext* const expCtx,
std::string init,
std::string accumulate,
std::string merge,
boost::optional<std::string> finalize)
: AccumulatorState(expCtx),
_init(std::move(init)),
_accumulate(std::move(accumulate)),
_merge(std::move(merge)),
_finalize(std::move(finalize)) {
resetMemUsageBytes();
}
void resetMemUsageBytes();
void incrementMemUsageBytes(size_t bytes);
// static arguments
std::string _init, _accumulate, _merge;
boost::optional<std::string> _finalize;
// accumulator state during execution
// 1. Initially, _state is empty.
// 2. On .startNewGroup(...), _state becomes the result of the user's init function.
// 3. On .processInternal(...), instead of calling the user's accumulate or merge function right
// away, we push_back the argument into _pendingCalls to be processed later. This is an
// optimization to reduce the number of calls into the JS engine.
// 4. On .getValue(), we process all the _pendingCalls and update the _state.
// 5. On .reset(), _state becomes empty again.
boost::optional<Value> _state;
// Each element is an input passed to processInternal.
std::vector<Value> _pendingCalls;
// True means the elements of _pendingCalls should be interpreted as intermediate states from
// other instances of $accumulator. False means the elements of _pendingCalls should be
// interpreted as inputs from accumulateArgs.
bool _pendingCallsMerging;
// Call the user's accumulate/merge function for each element of _pendingCalls.
void reducePendingCalls();
};
} // namespace mongo
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