How to update first element in array object

April 22, 2024

My document is

{
  _id: 1,
  age: "young",
  hobby: [
  {
    vehicle: "car",
    velocity: "fast"
  },
  {
    vehicle: "motorcycle",
    velocity: "fast"
  }
  ]
}

My goal is: when age became old, first hobby became "slow" but others remain "fast"

My code is:

mongoTemplate.updateFirst(
  Query.query(where("_id").is("1")),
    Update.update("age", "old")
      .set("hobby.$[elem].velocity", "slow")
      .filterArray(Criteria.where("elem").is(0)), "collection name")

But it does not work, result is:

{
  _id: 1,
  age: "old",
  hobby: [
  {
    vehicle: "car",
    velocity: "fast"  <<--- not slow
  },
  {
    vehicle: "motorcycle",
    velocity: "fast"
  }
  ]
}

I could achieve my goal with

mongoTemplate.updateFirst(
  Query.query(where("_id").is("1111")),
    Update.update("age", "old")
      .set("hobby.$[elem].velocity", "slow")
      .filterArray(Criteria.where("elem.vehicle").is("car")), "collection name")

But I want modify FIRST array element, not car array element

>Solution :

If you always only want to update the first element, then you can refer to the first element with 0. The standard query would be:

db.collection.update({ _id: 1111 },
{
  $set: {
    "age": "old",
    "hobby.0.velocity": "slow"  // note the '0'
  }
})

Mongo Playground

I don’t know spring but I presume the query would be something like:

mongoTemplate.updateFirst(
  Query.query(where("_id").is("1111")),
    Update.update("age", "old")
      .set("hobby.0.velocity", "slow")  // note the '0'