While debugging a problem in an app I found that it is caused by a wrong value returned from Mongo. So I end up have a collection for which .count() always returns 136 while the collection is empty.

Here is what I see in the mongo terminal:

> db.ReadStats.findOne() — normal collection
null
> db.ReadStats.count()
0
> db.PendingRecords.findOne() — broken collection?
null
> db.PendingRecords.count()
136

When I do dump — this collection is saved as PendingRecords.bson 0 B file. So it is really empty. And according to our log of logic actions, it really should be empty.

> db.repairDatabase()
{ "ok" : 1 }
> db.PendingRecords.count()
0

Repair helped, but what could go wrong? What should we do to do not encounter this again? Because it just breaks our app (