mirror of https://gitee.com/bigwinds/arangodb
115 lines
3.7 KiB
C++
115 lines
3.7 KiB
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_CONST_FETCHER_H
|
|
#define ARANGOD_AQL_CONST_FETCHER_H
|
|
|
|
#include "Aql/ExecutionState.h"
|
|
#include "Aql/InputAqlItemRow.h"
|
|
|
|
#include <memory>
|
|
|
|
namespace arangodb {
|
|
namespace aql {
|
|
|
|
class AqlItemBlock;
|
|
template <bool>
|
|
class DependencyProxy;
|
|
|
|
/**
|
|
* @brief Interface for all AqlExecutors that do only need one
|
|
* row at a time in order to make progress.
|
|
* The guarantee is the following:
|
|
* If fetchRow returns a row the pointer to
|
|
* this row stays valid until the next call
|
|
* of fetchRow.
|
|
*/
|
|
class ConstFetcher {
|
|
using DependencyProxy = aql::DependencyProxy<true>;
|
|
|
|
public:
|
|
explicit ConstFetcher(DependencyProxy& executionBlock);
|
|
TEST_VIRTUAL ~ConstFetcher() = default;
|
|
|
|
protected:
|
|
// only for testing! Does not initialize _dependencyProxy!
|
|
ConstFetcher();
|
|
|
|
public:
|
|
/**
|
|
* @brief Fetch one new AqlItemRow from upstream.
|
|
* **Guarantee**: the pointer returned is valid only
|
|
* until the next call to fetchRow.
|
|
*
|
|
* @return A pair with the following properties:
|
|
* ExecutionState:
|
|
* WAITING => IO going on, immediatly return to caller.
|
|
* DONE => No more to expect from Upstream, if you are done with
|
|
* this row return DONE to caller.
|
|
* HASMORE => There is potentially more from above, call again if
|
|
* you need more input.
|
|
* AqlItemRow:
|
|
* If WAITING => Do not use this Row, it is a nullptr.
|
|
* If HASMORE => The Row is guaranteed to not be a nullptr.
|
|
* If DONE => Row can be a nullptr (nothing received) or valid.
|
|
*/
|
|
TEST_VIRTUAL std::pair<ExecutionState, InputAqlItemRow> fetchRow();
|
|
TEST_VIRTUAL std::pair<ExecutionState, size_t> skipRows(size_t);
|
|
void injectBlock(SharedAqlItemBlockPtr block);
|
|
|
|
// Argument will be ignored!
|
|
std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t);
|
|
|
|
std::pair<ExecutionState, size_t> preFetchNumberOfRows(size_t atMost) {
|
|
// This is not implemented for this fetcher
|
|
TRI_ASSERT(false);
|
|
THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
|
|
}
|
|
|
|
private:
|
|
/**
|
|
* @brief Input block currently in use. Used for memory management by the
|
|
* ConstFetcher. May be moved if the Fetcher implementations
|
|
* are moved into separate classes.
|
|
*/
|
|
SharedAqlItemBlockPtr _currentBlock;
|
|
|
|
SharedAqlItemBlockPtr _blockForPassThrough;
|
|
|
|
/**
|
|
* @brief Index of the row to be returned next by fetchRow(). This is valid
|
|
* iff _currentBlock != nullptr and it's smaller or equal than
|
|
* _currentBlock->size(). May be moved if the Fetcher implementations
|
|
* are moved into separate classes.
|
|
*/
|
|
size_t _rowIndex;
|
|
|
|
private:
|
|
bool indexIsValid();
|
|
bool isLastRowInBlock();
|
|
};
|
|
|
|
} // namespace aql
|
|
} // namespace arangodb
|
|
|
|
#endif // ARANGOD_AQL_SINGLE_ROW_FETCHER_H
|