count() to be fast and efficient. In the mongo shell, this is true.
In C++, I wrote this:
mongocxx::client client; mongocxx::database db = MongoInit(client, ...); bsoncxx::document::view empty_filter; mongocxx::collection collection = db[collection_name]; int64_t collection_count = collection.count_documents(empty_filter);
This sometime takes a very long time. Am I doing something wrong?