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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/>.
*/
#include "mongo/db/index/hash_index_cursor.h"
#include <boost/scoped_ptr.hpp>
#include <vector>
#include "mongo/db/btreecursor.h"
#include "mongo/db/hasher.h"
#include "mongo/db/index/hash_access_method.h" // for HashAccessMethod::makeSingleKey
#include "mongo/db/index/index_cursor.h"
#include "mongo/db/pdfile.h"
#include "mongo/db/queryutil.h"
namespace mongo {
HashIndexCursor::HashIndexCursor(const string& hashedField, HashSeed seed, int hashVersion,
IndexDescriptor* descriptor)
: _hashedField(hashedField), _seed(seed), _hashVersion(hashVersion),
_descriptor(descriptor) { }
Status HashIndexCursor::setOptions(const CursorOptions& options) {
return Status::OK();
}
Status HashIndexCursor::seek(const BSONObj& position) {
//Use FieldRangeSet to parse the query into a vector of intervals
//These should be point-intervals if this cursor is ever used
//So the FieldInterval vector will be, e.g. <[1,1], [3,3], [6,6]>
FieldRangeSet frs( "" , position, true, true );
const vector<FieldInterval>& intervals = frs.range( _hashedField.c_str() ).intervals();
//Construct a new query based on the hashes of the previous point-intervals
//e.g. {a : {$in : [ hash(1) , hash(3) , hash(6) ]}}
BSONObjBuilder newQueryBuilder;
BSONObjBuilder inObj( newQueryBuilder.subobjStart( _hashedField ) );
BSONArrayBuilder inArray( inObj.subarrayStart("$in") );
vector<FieldInterval>::const_iterator i;
for( i = intervals.begin(); i != intervals.end(); ++i ){
if ( ! i->equality() ){
_oldCursor.reset(
BtreeCursor::make( nsdetails( _descriptor->parentNS()),
_descriptor->getOnDisk(),
BSON( "" << MINKEY ) ,
BSON( "" << MAXKEY ) ,
true ,
1 ) );
return Status::OK();
}
inArray.append(HashAccessMethod::makeSingleKey(i->_lower._bound, _seed, _hashVersion));
}
inArray.done();
inObj.done();
BSONObj newQuery = newQueryBuilder.obj();
BSONObjBuilder specBuilder;
BSONObjIterator it(_descriptor->keyPattern());
while (it.more()) {
BSONElement e = it.next();
specBuilder.append(e.fieldName(), 1);
}
BSONObj spec = specBuilder.obj();
//Use the point-intervals of the new query to create a Btree cursor
FieldRangeSet newfrs( "" , newQuery , true, true );
shared_ptr<FieldRangeVector> newVector(
new FieldRangeVector( newfrs , spec, 1 ) );
_oldCursor.reset(
BtreeCursor::make(nsdetails(_descriptor->parentNS()),
_descriptor->getOnDisk(),
newVector,
0,
1));
return Status::OK();
}
bool HashIndexCursor::isEOF() const { return _oldCursor->eof(); }
BSONObj HashIndexCursor::getKey() const { return _oldCursor->currKey(); }
DiskLoc HashIndexCursor::getValue() const { return _oldCursor->currLoc(); }
void HashIndexCursor::next() { _oldCursor->advance(); }
string HashIndexCursor::toString() { return _oldCursor->toString(); }
Status HashIndexCursor::savePosition() { _oldCursor->noteLocation(); return Status::OK(); }
Status HashIndexCursor::restorePosition() { _oldCursor->checkLocation(); return Status::OK(); }
} // namespace mongo
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