mongodb query by sub-field

Question

How to query all {"module" : "B"} ?

The following query doesn't work:

db.XXX.find({ "_id" : { "module" : "B" } }); 

Thanks a ton!

There data looks like:

{   "_id" : {"module" : "A","date" : ISODate("2013-03-18T07:00:00Z")},   "value" : {"count" : 1.0} }  {   "_id" : {"module" : "B","date" : ISODate("2013-03-18T08:00:00Z")},   "value" : {"count" : 2.0} } 

Answer 1

Try:

db.XXX.find({ "_id.module" :  "B" }); 

The difference is your original query would be trying to match on that entire subdocument (i.e. where _id is a subdocument containing a "module" field with value "B" and nothing else)

Reference: MongoDB Dot Notation

Answer 2

Use dot notation:

db.XXX.find({ "_id.module" : "B" })