[{"_id":"1","type":"bot","rooms":[{"_id":"6138e2b55c145846ec1e38c5","genre":"action"},{"_id":"6138e2b545c145846ec1e38c5","genre":"adventure"}]},{"_id":"2","type":"person","rooms":[{"_id":"6138e2565c145846ec1e38c5","genre":"food"},{"_id":"6138e2b5645c145846ec1e38c5","genre":"sport"}]},{"_id":"3","type":"duo","rooms":[{"_id":"6138e21c145846ec1e38c5","genre":"travel"},{"_id":"6138e35645c145846ec1e38c5","genre":"news"}]}]

db.collection.update({},{"$pull":{"rooms":{"_id":{"$in":["6138e21c145846ec1e38c5","6138e2565c145846ec1e38c5","6138e2b545c145846ec1e38c5"]}}}},{multi:true})