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/**
* Copyright (C) 2013-2014 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/exec/plan_stage.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/query/index_bounds.h"
#include "mongo/db/record_id.h"
#include "mongo/db/storage/index_entry_comparison.h"
#include "mongo/db/storage/sorted_data_interface.h"
#include "mongo/platform/unordered_set.h"
namespace mongo {
class IndexAccessMethod;
class IndexDescriptor;
class WorkingSet;
struct IndexScanParams {
IndexScanParams()
: descriptor(NULL), direction(1), doNotDedup(false), maxScan(0), addKeyMetadata(false) {}
const IndexDescriptor* descriptor;
IndexBounds bounds;
int direction;
bool doNotDedup;
// How many keys will we look at?
size_t maxScan;
// Do we want to add the key as metadata?
bool addKeyMetadata;
};
/**
* Stage scans over an index from startKey to endKey, returning results that pass the provided
* filter. Internally dedups on RecordId.
*
* Sub-stage preconditions: None. Is a leaf and consumes no stage data.
*/
class IndexScan : public PlanStage {
public:
/**
* Keeps track of what this index scan is currently doing so that it
* can do the right thing on the next call to work().
*/
enum ScanState {
// Need to initialize the underlying index traversal machinery.
INITIALIZING,
// Skipping keys as directed by the _checker.
NEED_SEEK,
// Retrieving the next key, and applying the filter if necessary.
GETTING_NEXT,
// The index scan is finished.
HIT_END
};
IndexScan(OperationContext* txn,
const IndexScanParams& params,
WorkingSet* workingSet,
const MatchExpression* filter);
virtual ~IndexScan() {}
virtual StageState work(WorkingSetID* out);
virtual bool isEOF();
virtual void doSaveState();
virtual void doRestoreState(OperationContext* opCtx);
virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
virtual StageType stageType() const {
return STAGE_IXSCAN;
}
virtual std::unique_ptr<PlanStageStats> getStats();
virtual const SpecificStats* getSpecificStats() const;
static const char* kStageType;
private:
/**
* Initialize the underlying index Cursor, returning first result if any.
*/
boost::optional<IndexKeyEntry> initIndexScan();
// transactional context for read locks. Not owned by us
OperationContext* _txn;
// The WorkingSet we fill with results. Not owned by us.
WorkingSet* const _workingSet;
// Index access.
const IndexAccessMethod* const _iam; // owned by Collection -> IndexCatalog
std::unique_ptr<SortedDataInterface::Cursor> _indexCursor;
const BSONObj _keyPattern;
// Keeps track of what work we need to do next.
ScanState _scanState;
// Contains expressions only over fields in the index key. We assume this is built
// correctly by whomever creates this class.
// The filter is not owned by us.
const MatchExpression* const _filter;
// Could our index have duplicates? If so, we use _returned to dedup.
bool _shouldDedup;
unordered_set<RecordId, RecordId::Hasher> _returned;
const bool _forward;
const IndexScanParams _params;
// Stats
IndexScanStats _specificStats;
//
// This class employs one of two different algorithms for determining when the index scan
// has reached the end:
//
//
// 1) If the index scan is not a single contiguous interval, then we use an
// IndexBoundsChecker to determine which keys to return and when to stop scanning.
// In this case, _checker will be non-NULL.
//
std::unique_ptr<IndexBoundsChecker> _checker;
IndexSeekPoint _seekPoint;
//
// 2) If the index scan is a single contiguous interval, then the scan can execute faster by
// letting the index cursor tell us when it hits the end, rather than repeatedly doing
// BSON compares against scanned keys. In this case _checker will be NULL.
//
// The key that the index cursor should stop on/after.
BSONObj _endKey;
// Is the end key included in the range?
bool _endKeyInclusive;
};
} // namespace mongo
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