Database
db={"resources":[{"_id":1,"repoId":1},{"_id":2,"repoId":10},{"_id":3,"repoId":2},{"_id":4,"repoId":50},{"_id":5,"repoId":100}],"RepositoryInfo":[{"_id":1},{"_id":2},{"_id":3},{"_id":4},{"_id":5}]}
Query
db.resources.aggregate([{"$lookup":{"from":"RepositoryInfo","localField":"repoId","foreignField":"_id","as":"repo"}},{"$match":{"repo":[]}}])