[{"title":"Java","uid":"1","_metadata":{"references":[]}},{"title":"Servlet","uid":"2","_metadata":{"references":[{"uid":"1"}]}},{"title":"JSP","uid":"3","_metadata":{"references":[{"uid":"2"},]}}]

db.collection.aggregate([{$match:{uid:"1"}},{"$graphLookup":{"from":"collection","startWith":"$uid","connectFromField":"uid","connectToField":"_metadata.references.uid","as":"matches"}},{$project:{uid:1,_metadata:{refrences:{$map:{input:"$matches",as:"match",in:{uid:"$$match.uid"}}}}}}])