包含不急于加载belongs_to

Question

我有两个型号

class Course
    belongs_to :content_picture
end

class ContentPicture
end

当我尝试加载课程并急切加载所有图片时，我得到N + 1个查询，我想在两个查询中进行此操作

我尝试过include，join，eager_load

结果：

Course.all

给出

 Course Load (1.4ms)  SELECT "courses".* FROM "courses"
  ContentPicture Load (1.4ms)  SELECT  "content_pictures".* FROM "content_pictures" WHERE "content_pictures"."id" = $1 LIMIT 1  [["id", 8]]
  ContentPicture Load (1.6ms)  SELECT  "content_pictures".* FROM "content_pictures" WHERE "content_pictures"."id" = $1 LIMIT 1  [["id", 7]]

包括：

Course.includes(:content_picture).all

结果：

Course.includes(:content_picture).all
  Course Load (1.6ms)  SELECT "courses".* FROM "courses"
  ContentPicture Load (1.1ms)  SELECT  "content_pictures".* FROM "content_pictures" WHERE "content_pictures"."id" = $1 LIMIT 1  [["id", 8]]
  ContentPicture Load (1.0ms)  SELECT  "content_pictures".* FROM "content_pictures" WHERE "content_pictures"."id" = $1 LIMIT 1  [["id", 7]]

随着加载和加入，它是一样的。

Answer 1

由于来自@MrYoshiji的暗示，我发现这是因为after_initialize阻止造成的

after_initialize do 
    self.content_picture ||= ContentPicture.new
end

删除块后，查询工作正常。

Answer 2

你会尝试这个

module.exports = { development: { client: 'pg', connection: 'postgres://localhost/eka_dev', migrations: { tableName: 'knex_migrations' } }, test: { client: 'pg', connection: 'postgres://localhost/eka_test', migrations: { tableName: 'knex_migrations' } }, production: { client: 'pg', connection: process.env.DATABASE_URL, migrations: { tableName: 'knex_migrations' } } };