mirror of https://gitee.com/bigwinds/arangodb
135 lines
4.3 KiB
C++
135 lines
4.3 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Tobias Gödderz
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGOD_AQL_ALL_ROWS_FETCHER_H
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#define ARANGOD_AQL_ALL_ROWS_FETCHER_H
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#include "Aql/AqlItemMatrix.h"
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#include "Aql/ExecutionState.h"
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#include <Basics/Exceptions.h>
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#include <memory>
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namespace arangodb {
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namespace aql {
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class AqlItemBlock;
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template <bool>
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class DependencyProxy;
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/**
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* @brief Interface for all AqlExecutors that do need all
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* rows at a time in order to make progress.
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*/
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class AllRowsFetcher {
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public:
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explicit AllRowsFetcher(DependencyProxy<false>& executionBlock);
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TEST_VIRTUAL ~AllRowsFetcher() = default;
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protected:
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// only for testing! Does not initialize _dependencyProxy!
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AllRowsFetcher() = default;
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public:
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/**
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* @brief Fetch one new AqlItemRow from upstream.
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* **Guarantee**: the pointer returned is valid only
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* until the next call to fetchRow.
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*
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* @return A pair with the following properties:
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* ExecutionState:
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* WAITING => IO going on, immediatly return to caller.
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* DONE => No more to expect from Upstream, if you are done with
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* this Matrix return DONE to caller.
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* HASMORE => Cannot be returned here
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*
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* AqlItemRow:
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* If WAITING => Do not use this Row, it is a nullptr.
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* If HASMORE => impossible
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* If DONE => Row can be a nullptr (nothing received) or valid.
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*/
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TEST_VIRTUAL std::pair<ExecutionState, AqlItemMatrix const*> fetchAllRows();
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// AllRowsFetcher cannot pass through. Could be implemented, but currently
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// there are no executors that could use this and not better use
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// SingleRowFetcher instead.
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std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t) {
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TRI_ASSERT(false);
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THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
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};
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/**
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* @brief Prefetch the number of rows that will be returned from upstream.
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* calling this function will render the fetchAllRows() a noop function
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* as this function will already fill the local result caches.
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*
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* @return A pair with the following properties:
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* ExecutionState:
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* WAITING => IO going on, immediatly return to caller.
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* DONE => No more to expect from Upstream, if you are done with
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* this Matrix return DONE to caller.
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* HASMORE => Cannot be returned here
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*
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* AqlItemRow:
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* If WAITING => Do not use this number, it is 0.
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* If HASMORE => impossible
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* If DONE => Number contains the correct number of rows upstream.
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*/
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TEST_VIRTUAL std::pair<ExecutionState, size_t> preFetchNumberOfRows(size_t);
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// only for ModificationNodes
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std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlockForModificationExecutor(std::size_t);
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// only for ModificationNodes
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ExecutionState upstreamState();
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private:
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DependencyProxy<false>* _dependencyProxy;
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std::unique_ptr<AqlItemMatrix> _aqlItemMatrix;
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ExecutionState _upstreamState;
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std::size_t _blockToReturnNext;
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private:
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/**
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* @brief Delegates to ExecutionBlock::getNrInputRegisters()
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*/
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RegisterId getNrInputRegisters() const;
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/**
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* @brief Delegates to ExecutionBlock::fetchBlock()
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*/
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std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlock();
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/**
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* @brief Fetch blocks from upstream until done
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*/
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ExecutionState fetchUntilDone();
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};
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} // namespace aql
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} // namespace arangodb
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#endif // ARANGOD_AQL_ALL_ROWS_FETCHER_H
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