rails eager loading for one-to-many association

Question

I have

class Article < ActiveRecord::Base
  has_one :template
end

and

class Template < ActiveRecord::Base
  has_many :articles
end

where Template model has got a room property. Now i'd like to build a list of all articles, where the articles template has a certain room value (say "bath").

I thought this is done by eager loading (resp: includes), but if i try

Article.includes(:template)

I get the error

SELECT "templates".* FROM "templates" WHERE "templates"."article_id" IN ('51', '52', '53', '54')
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR:  column templates.article_id does not exist
LINE 1: SELECT "templates".* FROM "templates" WHERE "templates"."art...

What am I doing wrong?

EDIT

here's my schema.rb as asked

# encoding: UTF-8
# This file is auto-generated from the current state of the database. Instead
# of editing this file, please use the migrations feature of Active Record to
# incrementally modify your database, and then regenerate this schema definition.
#
# Note that this schema.rb definition is the authoritative source for your
# database schema. If you need to create the application database on another
# system, you should be using db:schema:load, not running all the migrations
# from scratch. The latter is a flawed and unsustainable approach (the more migrations
# you'll amass, the slower it'll run and the greater likelihood for issues).
#
# It's strongly recommended that you check this file into your version control system.

ActiveRecord::Schema.define(version: 20160913122551) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "articles", force: :cascade do |t|
    t.string   "title"
    t.text     "details"
    t.integer  "value_eur"
    t.integer  "deposit_eur"
    t.integer  "location_id"
    t.integer  "user_id"
    t.datetime "created_at",    null: false
    t.datetime "updated_at",    null: false
    t.string   "picture"
    t.float    "rate_eur"
    t.string   "rate_interval"
    t.integer  "template_id"
    t.integer  "quality"
  end

  add_index "articles", ["location_id"], name: "index_articles_on_location_id", using: :btree
  add_index "articles", ["template_id"], name: "index_articles_on_template_id", using: :btree
  add_index "articles", ["user_id"], name: "index_articles_on_user_id", using: :btree

  create_table "locations", force: :cascade do |t|
    t.string   "street_and_no"
    t.string   "postcode"
    t.string   "city"
    t.string   "country"
    t.integer  "user_id"
    t.datetime "created_at",    null: false
    t.datetime "updated_at",    null: false
    t.float    "latitude"
    t.float    "longitude"
  end

  add_index "locations", ["user_id"], name: "index_locations_on_user_id", using: :btree

  create_table "templates", force: :cascade do |t|
    t.string   "title"
    t.text     "details_hint"
    t.float    "rate_eur"
    t.string   "rate_interval"
    t.string   "picture"
    t.datetime "created_at",    null: false
    t.datetime "updated_at",    null: false
    t.string   "room"
  end

  create_table "users", force: :cascade do |t|
    t.string   "email",                  default: "", null: false
    t.string   "encrypted_password",     default: "", null: false
    t.string   "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.integer  "sign_in_count",          default: 0,  null: false
    t.datetime "current_sign_in_at"
    t.datetime "last_sign_in_at"
    t.inet     "current_sign_in_ip"
    t.inet     "last_sign_in_ip"
    t.datetime "created_at",                          null: false
    t.datetime "updated_at",                          null: false
    t.string   "role"
    t.string   "nickname"
    t.string   "firstname"
    t.string   "lastname"
    t.string   "phoneno"
    t.boolean  "showemail"
    t.boolean  "showphone"
  end

  add_index "users", ["email"], name: "index_users_on_email", unique: true, using: :btree
  add_index "users", ["nickname"], name: "index_users_on_nickname", unique: true, using: :btree
  add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true, using: :btree

  add_foreign_key "articles", "locations"
  add_foreign_key "articles", "templates"
  add_foreign_key "articles", "users"
  add_foreign_key "locations", "users"
end

Answer 1

Your templates table does not have an article_id column according to the schema.rb you posted so you will need to create that reference.

Change

has_one :template 

in the articles model to

belongs_to :template