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arangodb/arangod/Aql/CalculationExecutor.h

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C++

////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
/// http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Jan Christoph Uhde
////////////////////////////////////////////////////////////////////////////////
#ifndef ARANGOD_AQL_CALACULATION_EXECUTOR_H
#define ARANGOD_AQL_CALACULATION_EXECUTOR_H
#include "Aql/ExecutionState.h"
#include "Aql/ExecutorInfos.h"
#include "Aql/InputAqlItemRow.h"
#include "Aql/SharedAqlItemBlockPtr.h"
#include "Aql/Stats.h"
#include "Aql/types.h"
#include <unordered_set>
#include <vector>
namespace arangodb {
namespace transaction {
class Methods;
}
namespace aql {
class Expression;
class OutputAqlItemRow;
class Query;
template<BlockPassthrough>
class SingleRowFetcher;
struct Variable;
struct CalculationExecutorInfos : public ExecutorInfos {
CalculationExecutorInfos(RegisterId outputRegister, RegisterId nrInputRegisters,
RegisterId nrOutputRegisters,
std::unordered_set<RegisterId> registersToClear,
std::unordered_set<RegisterId> registersToKeep, Query& query,
Expression& expression, std::vector<Variable const*>&& expInVars,
std::vector<RegisterId>&& expInRegs);
CalculationExecutorInfos() = delete;
CalculationExecutorInfos(CalculationExecutorInfos&&) = default;
CalculationExecutorInfos(CalculationExecutorInfos const&) = delete;
~CalculationExecutorInfos() = default;
RegisterId getOutputRegisterId() const noexcept;
Query& getQuery() const noexcept;
Expression& getExpression() const noexcept;
std::vector<Variable const*> const& getExpInVars() const noexcept;
std::vector<RegisterId> const& getExpInRegs() const noexcept;
private:
RegisterId _outputRegisterId;
Query& _query;
Expression& _expression;
std::vector<Variable const*> _expInVars; // input variables for expresseion
std::vector<RegisterId> _expInRegs; // input registers for expression
};
enum class CalculationType { Condition, V8Condition, Reference };
template <CalculationType calculationType>
class CalculationExecutor {
public:
struct Properties {
static constexpr bool preservesOrder = true;
static constexpr BlockPassthrough allowsBlockPassthrough = BlockPassthrough::Enable;
/* This could be set to true after some investigation/fixes */
static constexpr bool inputSizeRestrictsOutputSize = false;
};
using Fetcher = SingleRowFetcher<Properties::allowsBlockPassthrough>;
using Infos = CalculationExecutorInfos;
using Stats = NoStats;
CalculationExecutor(Fetcher& fetcher, CalculationExecutorInfos&);
~CalculationExecutor();
/**
* @brief produce the next Row of Aql Values.
*
* @return ExecutionState, and if successful exactly one new Row of AqlItems.
*/
std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
private:
// specialized implementations
void doEvaluation(InputAqlItemRow& input, OutputAqlItemRow& output);
// Only for V8Conditions
template <CalculationType U = calculationType, typename = std::enable_if_t<U == CalculationType::V8Condition>>
void enterContext();
// Only for V8Conditions
template <CalculationType U = calculationType, typename = std::enable_if_t<U == CalculationType::V8Condition>>
void exitContext();
[[nodiscard]] bool shouldExitContextBetweenBlocks() const;
private:
CalculationExecutorInfos& _infos;
Fetcher& _fetcher;
InputAqlItemRow _currentRow;
ExecutionState _rowState;
// true iff we entered a V8 context and didn't exit it yet.
// Necessary for owned contexts, which will not be exited when we call
// exitContext; but only for assertions in maintainer mode.
bool _hasEnteredContext;
};
} // namespace aql
} // namespace arangodb
#endif