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/**
* Copyright (C) 2013 10gen 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/>.
*/
#pragma once
#include <queue>
#include "mongo/db/btreecursor.h"
#include "mongo/db/geo/geoquery.h"
#include "mongo/db/geo/s2common.h"
#include "mongo/db/index/index_cursor.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pdfile.h"
#include "mongo/platform/unordered_set.h"
#include "third_party/s2/s2cap.h"
#include "third_party/s2/s2regionintersection.h"
namespace mongo {
class S2NearIndexCursor : public IndexCursor {
public:
S2NearIndexCursor(IndexDescriptor* descriptor, const S2IndexingParams& params);
virtual ~S2NearIndexCursor();
// Not implemented.
virtual Status seek(const BSONObj &position);
Status setOptions(const CursorOptions& options);
// Implemented:
// This is our very specific seek function. Not part of IndexCursor.
void seek(const BSONObj& query, const NearQuery& nearQuery,
const vector<GeoQuery>& regions);
virtual bool isEOF() const;
virtual BSONObj getKey() const;
virtual DiskLoc getValue() const;
virtual void next();
virtual string toString();
virtual Status savePosition();
virtual Status restorePosition();
// The geoNear command wants these.
long long nscanned() { return _stats._nscanned; }
double currentDistance() { return _results.top().distance; }
private:
// We use this to cache results of the search. Results are sorted to have decreasing
// distance, and callers are interested in loc and key.
struct Result {
Result(const DiskLoc& dl, const BSONObj& ck, double dist) : loc(dl), key(ck),
distance(dist) { }
bool operator<(const Result& other) const {
// We want increasing distance, not decreasing, so we reverse the <.
return distance > other.distance;
}
DiskLoc loc;
BSONObj key;
double distance;
};
/**
* Make the object that describes all keys that are within our current search annulus.
*/
BSONObj makeFRSObject();
/**
* Fill _results with all of the results in the annulus defined by _innerRadius and
* _outerRadius. If no results are found, grow the annulus and repeat until success (or
* until the edge of the world).
*/
void fillResults();
/**
* Grow _innerRadius and _outerRadius by _radiusIncrement, capping _outerRadius at halfway
* around the world (pi * _params.radius).
*/
void nextAnnulus();
double distanceTo(const BSONObj &obj);
IndexDescriptor* _descriptor;
// How we need/use the query:
// Matcher: Can have geo fields in it, but only with $within.
// This only really happens (right now) from geoNear command.
// We assume the caller takes care of this in the right way.
// FRS: No geo fields allowed!
// So, on that note: the query with the geo stuff taken out, used by makeFRSObject().
BSONObj _filteredQuery;
// The GeoQuery for the point we're doing near searching from.
NearQuery _nearQuery;
// What geo regions are we looking for?
vector<GeoQuery> _indexedGeoFields;
// How were the keys created? We need this to search for the right stuff.
S2IndexingParams _params;
// We also pass this to the FieldRangeVector ctor.
BSONObj _specForFRV;
// Geo-related variables.
// At what min distance (arc length) do we start looking for results?
double _minDistance;
// What's the max distance (arc length) we're willing to look for results?
double _maxDistance;
// We compute an annulus of results and cache it here.
priority_queue<Result> _results;
// These radii define the annulus we're currently looking at.
double _innerRadius;
double _outerRadius;
// When we search the next annulus, what to adjust our radius by? Grows when we search an
// annulus and find no results.
double _radiusIncrement;
// What have we returned already?
unordered_set<DiskLoc, DiskLoc::Hasher> _returned;
struct Stats {
Stats() : _nscanned(0), _matchTested(0), _geoMatchTested(0), _numShells(0),
_keyGeoSkip(0), _returnSkip(0), _btreeDups(0), _inAnnulusTested(0),
_numReturned(0) {}
// Stat counters/debug information goes below.
// How many items did we look at in the btree?
long long _nscanned;
// How many did we try to match?
long long _matchTested;
// How many did we geo-test?
long long _geoMatchTested;
// How many search shells did we use?
long long _numShells;
// How many did we skip due to key-geo check?
long long _keyGeoSkip;
long long _returnSkip;
long long _btreeDups;
long long _inAnnulusTested;
long long _numReturned;
};
Stats _stats;
// The S2 machinery that represents the search annulus
S2Cap _innerCap;
S2Cap _outerCap;
S2RegionIntersection _annulus;
// This is the "array index" of the key field that is the near field. We use this to do
// cheap is-this-doc-in-the-annulus testing.
int _nearFieldIndex;
// The max distance we've returned so far.
double _returnedDistance;
};
} // namespace mongo
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