working on nested arrays in mongodb

nested_arrays_mongodb.js

/*
{
  name,
  tags: [{
    name,
    subtags: [{
      name
    }]
  }]
}
*/

// create indexes for this structure
db.test.createIndex({ name: 1, 'tags.name': 1, 'tags.subtags.name': 1 })

// push tags
db.test.update({ name: 10 }, {
  $push: {
    tags: {
      $each: [{ name: 2 }, { name: 3 }, { name: 6 }]
    }    
  }
})

// push subtags placed in tag matched by name
db.test.update({ name: 10, 'tags.name': 14 }, {
  $push: {
    'tags.$.subtags': {
      $each: [{ name: 3 }, { name: 4 }, { name: 5 }]
    }    
  }
})

// find value placed in subtags
db.test.find({ name: 10, 'tags.name': 20, 'tags.subtags.name': 30 })

// update subtags' value (name) mathed by query
db.test.update(
   { name: 10 },
   { $inc: { "tags.$[t].subtags.$[s].name": 2 } },
   { arrayFilters: [ { "t.name": 20 } , { "s.name": 40 } ] }
)

// update tags' specific (!) value
// { 'tags.$': { name: 15 } } (rewrite whole object itself)
db.test.update({ name: 10, 'tags.name': 14 }, {
  $set: {
    'tags.$.name': 15
  }
})