How in MongoDB to update objects in an array with new keys only?

Question

MongoDB

Given a collection of approximately the following documents:

{
  "book": "Dune",
  "persons": [
    {"name": "Leto", "age": 52},
    {"name": "Paul", "age": 15}
  ]
}

Is there a way to update the objects in the persons array by passing in only the new keys, as can be done with $set ? To get the output:

{
  "book": "Dune",
  "persons": [
    {"name": "Leto", "age": 52, "alive": false},
    {"name": "Paul", "age": 15, "alive": true}
  ]
}

Answer 1

for one entry

db.books.update( { "persons.name": "Leto" }, { $set: { "persons.$.alive": true }} );