Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"key":1,"a":[{"b":[2]},{"b":[1]},{"b":[1]}]},{"key":2}]
Query
db.collection.update({key:1,a:{$elemMatch:{b:1}}},{$push:{"a.$.b":{$each:[4]}}})
Result