保存后复合主键不更新

Question

这是构成我的问题基础的最小测试用例。为什么 user 保存正确，属性 user.id 没有更新？尝试在数据库中重新查找记录可以毫无问题地获取它，并且 id 属性已正确设置。

AFAICT，这不是尝试在 sqlite 中自动递增复合主键的问题。 uuid/PostgreSQL 组合也会出现同样的问题。该模式只有 id 作为主键，[ :account_id, :id ] 是一个单独的唯一索引。

#!/usr/bin/env ruby
gem "rails", "~> 5.0.2"
gem "composite_primary_keys"

require "active_record"
require "composite_primary_keys"

ActiveRecord::Base.establish_connection(
  adapter: "sqlite3",
  database: ":memory:"
)

ActiveRecord::Schema.define do
  create_table :accounts, force: true do |t|
  end

  create_table :users, force: true do |t|
    t.references :account
    t.index [ :account_id, :id ], unique: true
  end
end

class User < ActiveRecord::Base
  self.primary_keys = [ :account_id, :id ]
  belongs_to :account, inverse_of: :users
end

class Account < ActiveRecord::Base
  has_many :users, inverse_of: :account
end

account = Account.create!
puts "created account: #{account.inspect}"
user = account.users.build
puts "before user.save: #{user.inspect}"
user.save
puts "after user.save: #{user.inspect}"
puts "account.users.first: #{account.users.first.inspect}"

运行该脚本的结果是：

~/src
% ./cpk-test.rb
-- create_table(:accounts, {:force=>true})
   -> 0.0036s
-- create_table(:users, {:force=>true})
   -> 0.0009s
created account: #<Account id: 1>
before user.save: #<User id: nil, account_id: 1>
after user.save: #<User id: nil, account_id: 1>
account.users.first: #<User id: 1, account_id: 1>

第一次保存后 user.id 不应该是 [1,1] 吗？如果这是一个错误，我应该向谁报告？

Answer 1

SQLite 不支持复合主键的自动递增。您可能会在 SO 中找到相关问题：1, 2.

这是来自第二个 link 的@SingleNegationElimination 回答：

In sqlite, you only get autoincrement behavior when only one integer column is the primary key. composite keys prevent autoincrement from taking effect.

You can get a similar result by defining id as the only primary key, but then adding an additional unique constraint on id, col3.

并且 composite_primary_keys 保持这种逻辑。

这里也存在这样做的技巧：sqlite: multi-column primary key with an auto increment column

Answer 2

事实证明，答案很简单。 Rails 通常从创建中获取返回的主键并使用它更新模型。复合键不会自行重新加载，所以我必须这样做。基本上在 after_create 挂钩中使用 reload 中的逻辑来获取创建的记录并相应地更新属性。

#!/usr/bin/env ruby
gem "rails", "5.0.2"
gem "composite_primary_keys", "9.0.6"

require "active_record"
require "composite_primary_keys"

ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Schema.define do
  create_table :accounts, force: true    
  create_table :users, force: true do |t|
    t.integer :account_id, null: false
    t.string :email, null: false
    t.index [ :account_id, :id ], unique: true
    t.index [ :account_id, :email ], unique: true
  end
end

class User < ActiveRecord::Base
  self.primary_keys = [ :account_id, :id ]
  belongs_to :account, inverse_of: :users

  after_create do
    self.class.connection.clear_query_cache
    fresh_person = self.class.unscoped {
      self.class.find_by!(account: account, email: email)
    }
    @attributes = fresh_person.instance_variable_get('@attributes')
    @new_record = false
    self
  end
end

class Account < ActiveRecord::Base
  has_many :users, inverse_of: :account
end

account = Account.create!
user = account.users.build(email: "#{SecureRandom.hex(4)}@example.com")
puts "before save user: #{user.inspect}"
user.save
puts "after save user: #{user.inspect}"

现在：

% ./cpk-test.rb
-- create_table(:accounts, {:force=>true})
   -> 0.0045s
-- create_table(:users, {:force=>true})
   -> 0.0009s
before save user: #<User id: nil, account_id: 1, email: "a54c2385@example.com">
after save user: #<User id: 1, account_id: 1, email: "a54c2385@example.com">

保存后复合主键不更新

composite primary key not updating after save

ruby-on-rails

rails-activerecord

composite-primary-key