// ensure an index cannot be created on system.indexes
t = db.getSiblingDB("indexes_on_indexes");
printjson(t.system.indexes.getIndexes());
assert.eq(t.system.indexes.getIndexes().length, 0);
print("trying via ensureIndex");
assert.commandFailed(t.system.indexes.ensureIndex({_id:1}));
printjson(t.system.indexes.getIndexes());
assert.eq(t.system.indexes.getIndexes().length, 0);
print("trying via createIndex");
assert.throws(t.system.indexes.createIndex({_id:1}));
printjson(t.system.indexes.getIndexes());
assert.eq(t.system.indexes.getIndexes().length, 0);
print("trying via direct insertion");
assert.throws(t.system.indexes.insert({ v:1,
                                        key:{_id:1},
                                        ns: "indexes_on_indexes.system.indexes",
                                        name:"wontwork"}));
printjson(t.system.indexes.getIndexes());
assert.eq(t.system.indexes.getIndexes().length, 0);