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// fts_index_format.cpp
/**
* Copyright (C) 2012 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/pch.h"
#include "mongo/base/init.h"
#include "mongo/db/fts/fts_index_format.h"
namespace mongo {
namespace fts {
namespace {
BSONObj nullObj;
BSONElement nullElt;
}
MONGO_INITIALIZER( FTSIndexFormat )( InitializerContext* context ) {
BSONObjBuilder b;
b.appendNull( "" );
nullObj = b.obj();
nullElt = nullObj.firstElement();
return Status::OK();
}
void FTSIndexFormat::getKeys( const FTSSpec& spec,
const BSONObj& obj,
BSONObjSet* keys ) {
int extraSize = 0;
vector<BSONElement> extrasBefore;
vector<BSONElement> extrasAfter;
// compute the non FTS key elements
for ( unsigned i = 0; i < spec.numExtraBefore(); i++ ) {
BSONElement e = obj.getFieldDotted(spec.extraBefore(i));
if ( e.eoo() )
e = nullElt;
uassert( 16675, "cannot have a multi-key as a prefix to a text index",
e.type() != Array );
extrasBefore.push_back(e);
extraSize += e.size();
}
for ( unsigned i = 0; i < spec.numExtraAfter(); i++ ) {
BSONElement e = obj.getFieldDotted(spec.extraAfter(i));
if ( e.eoo() )
e = nullElt;
extrasAfter.push_back(e);
extraSize += e.size();
}
TermFrequencyMap term_freqs;
spec.scoreDocument( obj, &term_freqs );
// create index keys from raw scores
// only 1 per string
for ( TermFrequencyMap::const_iterator i = term_freqs.begin();
i != term_freqs.end();
++i ) {
const string& term = i->first;
double weight = i->second;
// guess the total size of the btree entry based on the size of the weight, term tuple
int guess =
5 /* bson overhead */ +
10 /* weight */ +
8 /* term overhead */ +
term.size() +
extraSize;
BSONObjBuilder b(guess); // builds a BSON object with guess length.
for ( unsigned k = 0; k < extrasBefore.size(); k++ )
b.appendAs( extrasBefore[k], "" );
_appendIndexKey( b, weight, term );
for ( unsigned k = 0; k < extrasAfter.size(); k++ )
b.appendAs( extrasAfter[k], "" );
BSONObj res = b.obj();
verify( guess >= res.objsize() );
keys->insert( res );
}
}
BSONObj FTSIndexFormat::getIndexKey( double weight,
const string& term,
const BSONObj& indexPrefix ) {
BSONObjBuilder b;
BSONObjIterator i( indexPrefix );
while ( i.more() )
b.appendAs( i.next(), "" );
_appendIndexKey( b, weight, term );
return b.obj();
}
void FTSIndexFormat::_appendIndexKey( BSONObjBuilder& b, double weight, const string& term ) {
verify( weight >= 0 && weight <= MAX_WEIGHT ); // FTSmaxweight = defined in fts_header
b.append( "", term );
b.append( "", weight );
}
}
}
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