I am using MongoDB 2.6 standard. I have successfully created multiple collections, inserted data, queried data, etc. Works fine inside of the Mongo shell, as well as from NodeJS apps using MongoSkin. So far, so good. Now I need to use a third-party tool (D2RQ) to access the data. It appears that D2RQ uses the _schema collection to obtain collection names, column names, data types, and so on. D2RQ works for three of the collections because the collections are in _schema in MongoDB. A fourth collection is not in _schema and seems to be invisible. However, the fourth collection is present in MongoDB. The collection has data. I can query the collection in the Mongo shell, and from NodeJS using Mongoskin. Any idea why the collection is not appearing in _schema? Is this a MongoDB bug?