sorting - Why does MongoDB sort return empty names for ascending sorted documents? -

i have simple collection of restaurants (from mongodb documentation). 1 of fields “name”. can find names of restaurants follows:

db.restaurants.find({}, {"name" : 1, "_id" : 0});

if try sort descending order, i.e.,

db.restaurants.find({}, {"name" : 1, "_id" : 0}).sort({"name":-1});

everything comes out fine:

{ "name" : "zz's pizza & grill" } { "name" : "zz clam bar" } ...

however, if try sort ascending order:

db.restaurants.find({}, {"name" : 1, "_id" : 0}).sort({"name":1});

i get

{ "name" : "" } { "name" : "" } ...

what's odd if add other keys sort argument before "name", ascending sort properly, i.e.

db.restaurants.find({}, {"name" : 1, "_id" : 0}).sort({"cuisine":1, "name":1});

what gives? insights!

RT