Mongoengine, retriving only some of a MapField

Question

For Example.. In Mongodb..

> db.test.findOne({}, {'mapField.FREE':1})
{
    "_id" : ObjectId("4fb7b248c450190a2000006a"),
    "mapField" : {
            "BOXFLUX" : {
                    "a" : "f",
            }
    }
}

The 'mapField' field is made of MapField of Mongoengine. and 'mapField' field has a log of key and data.. but I just retrieved only 'BOXFLUX'..

this query is not working in MongoEngine.... for example..

BoxfluxDocument.objects( ~~ querying ~~ ).only('mapField.BOXFLUX')

AS you can see.. only('mapField.BOXFLUX') or only only('mapField__BOXFLUX') does not work. it retrieves all 'mapField' data, including 'BOXFLUX' one..

How can I retrieve only a field of MapField???

Answer 1

Try this:

query = BlogPost.objects({your: query})
if name:
    query = query.only('author__'+name)
else:
    query = query.only('author')