Value DocumentSourceCursor::serialize(bool explain) const {
// we never parse a documentSourceCursor, so we only serialize for explain
if (!explain)
return Value();
Lock::DBRead lk(ns);
Client::Context ctx(ns, storageGlobalParams.dbpath, /*doVersion=*/false);
ClientCursorPin pin(_cursorId);
ClientCursor* cursor = pin.c();
uassert(17135, "Cursor deleted. Was the collection or database dropped?",
cursor);
cursor->c()->recoverFromYield();
return Value(DOC(getSourceName() <<
DOC("query" << Value(_query)
<< "sort" << (!_sort.isEmpty() ? Value(_sort) : Value())
<< "limit" << (_limit ? Value(_limit->getLimit()) : Value())
<< "fields" << (_projection ? Value(_projection->getSpec()) : Value())
<< "indexOnly" << canUseCoveredIndex(cursor)
<< "cursorType" << cursor->c()->toString()
))); // TODO get more plan information
}
void DocumentSourceCursor::findNext() {
if ( !_cursorWithContext ) {
pCurrent.reset();
return;
}
for( ; cursor()->ok(); cursor()->advance() ) {
yieldSometimes();
if ( !cursor()->ok() ) {
// The cursor was exhausted during the yield.
break;
}
if ( !cursor()->currentMatches() || cursor()->currentIsDup() )
continue;
// grab the matching document
BSONObj documentObj;
if (canUseCoveredIndex()) {
// Can't have a Chunk Manager if we are here
documentObj = cursor()->c()->keyFieldsOnly()->hydrate(cursor()->currKey());
}
else {
documentObj = cursor()->current();
// check to see if this is a new object we don't own yet
// because of a chunk migration
if ( chunkMgr() && ! chunkMgr()->belongsToMe(documentObj) )
continue;
if (_projection) {
documentObj = _projection->transform(documentObj);
}
}
pCurrent = Document::createFromBsonObj(
&documentObj, NULL /* LATER pDependencies.get()*/);
cursor()->advance();
return;
}
// If we got here, there aren't any more documents.
// The CursorWithContext (and its read lock) must be released, see SERVER-6123.
dispose();
pCurrent.reset();
}
void DocumentSourceCursor::yieldSometimes() {
try { // SERVER-5752 may make this try unnecessary
// if we are index only we don't need the recored
bool cursorOk = cursor()->yieldSometimes(canUseCoveredIndex()
? ClientCursor::DontNeed
: ClientCursor::WillNeed);
uassert( 16028, "collection or database disappeared when cursor yielded", cursorOk );
}
catch(SendStaleConfigException& e){
// We want to ignore this because the migrated documents will be filtered out of the
// cursor anyway and, we don't want to restart the aggregation after every migration.
log() << "Config changed during aggregation - command will resume" << endl;
// useful for debugging but off by default to avoid looking like a scary error.
LOG(1) << "aggregation stale config exception: " << e.what() << endl;
}
}
void DocumentSourceCursor::loadBatch() {
if (!_cursorId) {
dispose();
return;
}
// We have already validated the sharding version when we constructed the cursor
// so we shouldn't check it again.
Lock::DBRead lk(ns);
Client::Context ctx(ns, storageGlobalParams.dbpath, /*doVersion=*/false);
ClientCursorPin pin(_cursorId);
ClientCursor* cursor = pin.c();
uassert(16950, "Cursor deleted. Was the collection or database dropped?",
cursor);
cursor->c()->recoverFromYield();
int memUsageBytes = 0;
for( ; cursor->ok(); cursor->advance() ) {
yieldSometimes(cursor);
if ( !cursor->ok() ) {
// The cursor was exhausted during the yield.
break;
}
if ( !cursor->currentMatches() || cursor->currentIsDup() )
continue;
// grab the matching document
if (canUseCoveredIndex(cursor)) {
// Can't have collection metadata if we are here
BSONObj indexKey = cursor->currKey();
_currentBatch.push_back(Document(cursor->c()->keyFieldsOnly()->hydrate(indexKey)));
}
else {
BSONObj next = cursor->current();
// check to see if this is a new object we don't own yet
// because of a chunk migration
if (_collMetadata) {
KeyPattern kp( _collMetadata->getKeyPattern() );
if ( !_collMetadata->keyBelongsToMe( kp.extractSingleKey( next ) ) ) continue;
}
_currentBatch.push_back(_projection
? documentFromBsonWithDeps(next, _dependencies)
: Document(next));
}
if (_limit) {
if (++_docsAddedToBatches == _limit->getLimit()) {
break;
}
verify(_docsAddedToBatches < _limit->getLimit());
}
memUsageBytes += _currentBatch.back().getApproximateSize();
if (memUsageBytes > MaxBytesToReturnToClientAtOnce) {
// End this batch and prepare cursor for yielding.
cursor->advance();
if (cursor->c()->supportYields()) {
ClientCursor::YieldData data;
cursor->prepareToYield(data);
} else {
cursor->c()->noteLocation();
}
return;
}
}
// If we got here, there aren't any more documents.
// The Cursor must be released, see SERVER-6123.
pin.release();
ClientCursor::erase(_cursorId);
_cursorId = 0;
_collMetadata.reset();
}
void DocumentSourceCursor::findNext() {
unstarted = false;
if ( !_cursorWithContext ) {
pCurrent = Document();
hasCurrent = false;
return;
}
for( ; cursor()->ok(); cursor()->advance() ) {
yieldSometimes();
if ( !cursor()->ok() ) {
// The cursor was exhausted during the yield.
break;
}
if ( !cursor()->currentMatches() || cursor()->currentIsDup() )
continue;
// grab the matching document
if (canUseCoveredIndex()) {
// Can't have collection metadata if we are here
BSONObj indexKey = cursor()->currKey();
pCurrent = Document(cursor()->c()->keyFieldsOnly()->hydrate(indexKey));
}
else {
BSONObj next = cursor()->current();
// check to see if this is a new object we don't own yet
// because of a chunk migration
if (collMetadata()) {
KeyPattern kp( collMetadata()->getKeyPattern() );
if ( !collMetadata()->keyBelongsToMe( kp.extractSingleKey( next ) ) ) continue;
}
if (!_projection) {
pCurrent = Document(next);
}
else {
pCurrent = documentFromBsonWithDeps(next, _dependencies);
if (debug && !_dependencies.empty()) {
// Make sure we behave the same as Projection. Projection doesn't have a
// way to specify "no fields needed" so we skip the test in that case.
MutableDocument byAggo(pCurrent);
MutableDocument byProj(Document(_projection->transform(next)));
if (_dependencies["_id"].getType() == Object) {
// We handle subfields of _id identically to other fields.
// Projection doesn't handle them correctly.
byAggo.remove("_id");
byProj.remove("_id");
}
if (Document::compare(byAggo.peek(), byProj.peek()) != 0) {
PRINT(next);
PRINT(_dependencies);
PRINT(_projection->getSpec());
PRINT(byAggo.peek());
PRINT(byProj.peek());
verify(false);
}
}
}
}
hasCurrent = true;
cursor()->advance();
return;
}
// If we got here, there aren't any more documents.
// The CursorWithContext (and its read lock) must be released, see SERVER-6123.
dispose();
pCurrent = Document();
hasCurrent = false;
}