Major - P3 Using mongo v2.0.8, I created two collections, a.counter and b.counter, and then ran mongodump v2.0.8 w/o specifying a database. The observed behavior is mongodump iterating through all databases and looks for the "counter" collection.
/tmp> /opt/mongodb-osx-x86_64-2.0.8/bin/mongodump --port 12345 -c counter connected to: 127.0.0.1:12345 all dbs DATABASE: a to dump/a a.counter to dump/a/counter.bson 1000 objects DATABASE: b to dump/b b.counter to dump/b/counter.bson 1000 objects DATABASE: * to dump/*
mongodump v2.2.1 results in:
/tmp> /opt/mongodb-osx-x86_64-2.2.1/bin/mongodump --port 12345 -c counter
connected to: 127.0.0.1:12345
Tue Nov 20 10:25:16 all dbs
assertion: 13106 nextSafe(): { $err: "db name can't be empty", code: 13075 }
This seems like a regression, or at minimum, an undocumented change in behavior.