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/* scanandorder.h
Order results (that aren't already indexes and in order.)
*/
/**
* Copyright (C) 2008 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 "mongo/db/indexkey.h"
#include "mongo/db/projection.h"
#include "mongo/db/queryutil.h"
namespace mongo {
class ParsedQuery;
static const int ScanAndOrderMemoryLimitExceededAssertionCode = 10128;
class KeyType : boost::noncopyable {
public:
BSONObj _keyPattern;
FieldRangeVector _keyCutter;
public:
KeyType(const BSONObj &pattern, const FieldRangeSet &frs)
: _keyPattern(pattern), _keyCutter(frs, pattern, 1) {
verify(!pattern.isEmpty());
}
/**
* @return first key of the object that would be encountered while
* scanning an index with keySpec 'pattern' using constraints 'frs', or
* BSONObj() if no such key.
*/
BSONObj getKeyFromObject(const BSONObj &o) const {
return _keyCutter.firstMatch(o);
}
};
/* todo:
_ response size limit from runquery; push it up a bit.
*/
inline void fillQueryResultFromObj(BufBuilder& bb, const Projection *filter, const BSONObj& js,
const MatchDetails* details = NULL,
const DiskLoc* loc=NULL) {
if ( filter ) {
BSONObjBuilder b( bb );
filter->transform( js , b, details );
if (loc)
b.append("$diskLoc", loc->toBSONObj());
b.done();
}
else if (loc) {
BSONObjBuilder b( bb );
b.appendElements(js);
b.append("$diskLoc", loc->toBSONObj());
b.done();
}
else {
bb.appendBuf((void*) js.objdata(), js.objsize());
}
}
typedef multimap<BSONObj,BSONObj,BSONObjCmp> BestMap;
class ScanAndOrder {
public:
static const unsigned MaxScanAndOrderBytes;
ScanAndOrder(int startFrom, int limit, const BSONObj &order, const FieldRangeSet &frs) :
_best( BSONObjCmp( order ) ),
_startFrom(startFrom), _order(order, frs) {
_limit = limit > 0 ? limit + _startFrom : 0x7fffffff;
_approxSize = 0;
}
int size() const { return _best.size(); }
/**
* @throw ScanAndOrderMemoryLimitExceededAssertionCode if adding would grow memory usage
* to ScanAndOrder::MaxScanAndOrderBytes.
*/
void add(const BSONObj &o, const DiskLoc* loc);
/* scanning complete. stick the query result in b for n objects. */
void fill(BufBuilder& b, const ParsedQuery *query, int& nout) const;
/** Functions for testing. */
protected:
unsigned approxSize() const { return _approxSize; }
private:
void _add(const BSONObj& k, const BSONObj& o, const DiskLoc* loc);
void _addIfBetter(const BSONObj& k, const BSONObj& o, const BestMap::iterator& i,
const DiskLoc* loc);
/**
* @throw ScanAndOrderMemoryLimitExceededAssertionCode if approxSize would grow too high,
* otherwise update _approxSize.
*/
void _validateAndUpdateApproxSize( const int approxSizeDelta );
BestMap _best; // key -> full object
int _startFrom;
int _limit; // max to send back.
KeyType _order;
unsigned _approxSize;
};
} // namespace mongo
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