Mongo client can't access collections prefixed with an underscore

Question

I named a collection with an underscore in Mongo, and can't access it from the shell:

meteor:PRIMARY> show collections _assignments chatmessages (... other stuff) 

Trying to run any function on the first collection results in an error:

meteor:PRIMARY> db._assignments.find() Thu Jun 19 10:53:28.450 TypeError: Cannot call method 'find' of undefined 

However, other collections work fine:

meteor:PRIMARY> db.chatmessages.find() { "room" : "j5oau9DJ6GNpT9nR8", "userId" : "at9Kt8NNL4aeof6LE", "text" : "@nomad943 can you take a look at event #1?", "timestamp" : 1391806611977, "_id" : "26GbXa6c4B65FYRxC" } { "room" : "T7JfjBhri48bNHAfQ", "userId" : "B82LxmPBZWDnN4N2p", "text" : "Thinking #60 should be deleted, it's a duplicate of #36 and the region is wrong for the province", "timestamp" : ISODate("2014-06-18T18:57:56.480Z"), "_id" : "29pKqPhi4hgxCb2Ky" } 

What's going on here?

Answer 1

I don't see the problem other than the shell cannot address this with it's default helper syntax. You can still access collections named like this in the shell:

db.createCollection("_assignments") { "ok" : 1 } db.getCollection("_assignments").find() db.getCollection("_assignments").insert({ "a": 1 }) WriteResult({ "nInserted" : 1 }) db.getCollection("_assignments").find({ "a": 1 }) { "_id" : ObjectId("53a36a4047234c4e9bb4feac"), "a" : 1 } 

Answer 2

This is a known bug. Don't prefix collections with underscores.

https://jira.mongodb.org/browse/SERVER-445