gistfile1.py

#### Pymongo 2.1.1
for uuid in list(uuids)[:1]:
    query = {
        "uuid" : uuid,
    }
    fields = {"period" : 1, "logs.hour": 1}

    for doc in db.logEventByHour.find({"uuid":uuid}, fields=fields):
        log.debug("doc: %r", doc)


#### Python output  (empty log subdocuments)
doc: {u'_id': ObjectId('XXXXXXXXXXXXXXXXXXXXXXXXX'), u'logs': [{}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}], u'period': u'2012060622'}
doc: {u'_id': ObjectId('XXXXXXXXXXXXXXXXXXXXXXXXX'), u'logs': [{}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}], u'period': u'2012060621'}



#### Mongo 2.0.6 
db.logEventByHour.find({}, {"logs.hour":1})

#### Shell output (log.hour is present
{ "_id" : ObjectId("XXXXXXXXXXXXXXXXXXXXX"), "logs" : [      {       "hour" : 15 },  {       "hour" : 15 },  {       "hour" : 15 },  {       "hour" : 15 },  {       "hour" : 15 } ] }
...