Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{_id:1,tag:{k:"bar",v:"BAR"}},{_id:2,tag:{k:"baz",v:"BAZ"}}]
Query
db.collection.aggregate([{$match:{"tag.k":{$gte:"baz"}}},{$addFields:{tag:{$arrayToObject:[["$tag"]]}}}])
Result