// static
void HashAccessMethod::getKeysImpl(const BSONObj& obj, const string& hashedField, HashSeed seed,
int hashVersion, bool isSparse, BSONObjSet* keys) {
const char* cstr = hashedField.c_str();
BSONElement fieldVal = obj.getFieldDottedOrArray(cstr);
uassert(16766, "Error: hashed indexes do not currently support array values",
fieldVal.type() != Array );
if (!fieldVal.eoo()) {
BSONObj key = BSON( "" << makeSingleKey(fieldVal, seed, hashVersion));
keys->insert(key);
}
else if (!isSparse) {
BSONObj nullObj = BSON("" << BSONNULL);
keys->insert(BSON("" << makeSingleKey(nullObj.firstElement(), seed, hashVersion)));
}
}
void HashedIndexType::getKeys( const BSONObj &obj, BSONObjSet &keys ) const {
string hashedFieldCopy = string( _hashedField );
const char* hashedFieldCopyPtr = hashedFieldCopy.c_str();
BSONElement fieldVal = obj.getFieldDottedOrArray( hashedFieldCopyPtr );
uassert( 16244 , "Error: hashed indexes do not currently support array values" , fieldVal.type() != Array );
if ( ! fieldVal.eoo() ) {
BSONObj key = BSON( "" << makeSingleKey( fieldVal , _seed , _hashVersion ) );
keys.insert( key );
}
else if (! _isSparse ) {
BSONObj nullobj = BSON( _hashedField << BSONNULL );
BSONElement nullElt = nullobj.firstElement();
BSONObj key = BSON( "" << makeSingleKey( nullElt , _seed , _hashVersion ) );
keys.insert( key );
}
}
void HashAccessMethod::getKeys(const BSONObj& obj, BSONObjSet* keys) {
const char* cstr = _hashedField.c_str();
BSONElement fieldVal = obj.getFieldDottedOrArray(cstr);
uassert(16766, "Error: hashed indexes do not currently support array values",
fieldVal.type() != Array );
if (!fieldVal.eoo()) {
BSONObj key = BSON( "" << makeSingleKey( fieldVal , _seed , _hashVersion ) );
keys->insert( key );
} else if (!_descriptor->isSparse()) {
keys->insert( _missingKey.copy() );
}
}
shared_ptr<Cursor> HashedIndexType::newCursor( const BSONObj& query ,
const BSONObj& order , int numWanted ) const {
//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( "" , query , true, true );
const vector<FieldInterval>& intervals = frs.range( _hashedField.c_str() ).intervals();
//Force a match of the query against the actual document by giving
//the cursor a matcher with an empty indexKeyPattern. This insures the
//index is not used as a covered index.
//NOTE: this forcing is necessary due to potential hash collisions
const shared_ptr< CoveredIndexMatcher > forceDocMatcher(
new CoveredIndexMatcher( query , BSONObj() ) );
//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() ){
const shared_ptr< BtreeCursor > exhaustiveCursor(
BtreeCursor::make( nsdetails( _spec->getDetails()->parentNS().c_str()),
*( _spec->getDetails() ),
BSON( "" << MINKEY ) ,
BSON( "" << MAXKEY ) ,
true ,
1 ) );
exhaustiveCursor->setMatcher( forceDocMatcher );
return exhaustiveCursor;
}
inArray.append( makeSingleKey( i->_lower._bound , _seed , _hashVersion ) );
}
inArray.done();
inObj.done();
BSONObj newQuery = newQueryBuilder.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 ) );
const shared_ptr< BtreeCursor > cursor(
BtreeCursor::make( nsdetails( _spec->getDetails()->parentNS().c_str()),
*( _spec->getDetails() ), newVector , 1 ) );
cursor->setMatcher( forceDocMatcher );
return cursor;
}
HashedIndexType::HashedIndexType( const IndexPlugin* plugin , const IndexSpec* spec ) :
IndexType( plugin , spec ) , _keyPattern( spec->keyPattern ) {
//change these if single-field limitation lifted later
uassert( 16241 , "Currently only single field hashed index supported." ,
_keyPattern.toBSON().nFields() == 1 );
uassert( 16242 , "Currently hashed indexes cannot guarantee uniqueness. Use a regular index." ,
! (spec->info).getField("unique").booleanSafe() );
//Default _seed to 0 if "seed" is not included in the index spec
//or if the value of "seed" is not a number
_seed = (spec->info).getField("seed").numberInt();
//Default _isSparse to false if "sparse" is not included in the index spec
//or if the value of "sparse" is not a boolean
_isSparse = (spec->info).getField("sparse").booleanSafe();
//In case we have hashed indexes based on other hash functions in
//the future, we store a hashVersion number. If hashVersion changes,
// "makeSingleKey" will need to change accordingly.
//Defaults to 0 if "hashVersion" is not included in the index spec
//or if the value of "hashversion" is not a number
_hashVersion = (spec->info).getField("hashVersion").numberInt();
//Get the hashfield name
BSONElement firstElt = spec->keyPattern.firstElement();
massert( 16243 , "error: no hashed index field" ,
firstElt.str().compare( HASHED_INDEX_TYPE_IDENTIFIER ) == 0 );
_hashedField = firstElt.fieldName();
// Explicit null valued fields and missing fields are both represented in hashed indexes
// using the hash value of the null BSONElement. This is partly for historical reasons
// (hash of null was used in the initial release of hashed indexes and changing would alter
// the data format). Additionally, in certain places the hashed index code and the index
// bound calculation code assume null and missing are indexed identically.
BSONObj nullObj = BSON( "" << BSONNULL );
_missingKey = BSON( "" << makeSingleKey( nullObj.firstElement(), _seed, _hashVersion ) );
}
HashAccessMethod::HashAccessMethod(IndexDescriptor* descriptor)
: BtreeBasedAccessMethod(descriptor) {
const string HASHED_INDEX_TYPE_IDENTIFIER = "hashed";
//change these if single-field limitation lifted later
uassert(16763, "Currently only single field hashed index supported." ,
1 == descriptor->getNumFields());
uassert(16764, "Currently hashed indexes cannot guarantee uniqueness. Use a regular index.",
!descriptor->unique());
//Default _seed to 0 if "seed" is not included in the index spec
//or if the value of "seed" is not a number
_seed = descriptor->getInfoElement("seed").numberInt();
//In case we have hashed indexes based on other hash functions in
//the future, we store a hashVersion number. If hashVersion changes,
// "makeSingleKey" will need to change accordingly.
//Defaults to 0 if "hashVersion" is not included in the index spec
//or if the value of "hashversion" is not a number
_hashVersion = descriptor->getInfoElement("hashVersion").numberInt();
//Get the hashfield name
BSONElement firstElt = descriptor->keyPattern().firstElement();
massert(16765, "error: no hashed index field",
firstElt.str().compare(HASHED_INDEX_TYPE_IDENTIFIER) == 0);
_hashedField = firstElt.fieldName();
// Explicit null valued fields and missing fields are both represented in hashed indexes
// using the hash value of the null BSONElement. This is partly for historical reasons
// (hash of null was used in the initial release of hashed indexes and changing would alter
// the data format). Additionally, in certain places the hashed index code and the index
// bound calculation code assume null and missing are indexed identically.
BSONObj nullObj = BSON("" << BSONNULL);
_missingKey = BSON("" << makeSingleKey(nullObj.firstElement(), _seed, _hashVersion));
}