Elasticsearch-model - trying to reference parent data to add to index

Question

I am using elasticsearch with rails for live search functionality on a twitter-like feed. I have a User table and a Post table that are stored in Postgres. I only want to index the Post table in ES for searching, however I want the User data for each post so I can show who made the post, what their rank is etc. So essentially I want to join the User and Post data, then index it into elasticsearch. Right now, my Post model looks like this:

class Post < ApplicationRecord
  belongs_to :user

  include Elasticsearch::Model
  include Elasticsearch::Model::Callbacks

  index_name Rails.application.class.parent_name.underscore

  settings index: { number_of_shards: 1 } do    
    mapping dynamic: false do
        indexes :title, analyzer: 'english'
        indexes :description, analyzer: 'english'
    end
  end

  def self.search(query)
    __elasticsearch__.search(
    {
        query: {
          multi_match: {
          query: query,
          type: 'phrase',
          fields: ['title^5', 'description']
        },
    }
    )
  end

My User model looks like this:

class User < ApplicationRecord
    has_many :posts
end

My schema looks like this:

ActiveRecord::Schema.define(version: 2020_04_16_175351) do
  create_table "posts", force: :cascade do |t|
    t.string "title"
    t.text "description"
    t.string "image"
    t.integer "vouches"
    t.bigint "user_id", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["user_id"], name: "index_posts_on_user_id"
  end

  create_table "users", force: :cascade do |t|
    t.string "name"
    t.string "username"
    t.integer "rank"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

  add_foreign_key "posts", "users"
end

And when I do an elasticsearch query on localhost:9200, each Post it returns is an object that looks like this:

{ "id": x , "title": "y" , "description": "z", "image": "", "vouches": 0, "user_id": 1}

I want to be able to have the relevant user object or user data stored in each post object - not just the user_id. Ideally I'd like to see a Post object that looks similar to this:

{ "id": x , "title": "y" , "description": "z", "image": "", "vouches": 0, "user_id": 1, "username": "a", "rank": 0...etc}

I feel like this should happen in the Post model somewhere but I've been unsuccessful in my attempt at using nested mapping among others.

Answer 1

So I was able to solve this using the 'as_indexed_json' method from elasticsearch-models. I just placed it in the Post model under the mappings.

def as_indexed_json(options = {})
  self.as_json(
    options.merge(
      only: [:id, :title, :body, :published_at, :created_at, :updated_at],
      include: { user: { only: [:id, :name] } }
    )
  )
end