Store message receivers in a new table instead of in a serializied value

db/migrate/20181201000100_create_message_recipients.foodsoft_messages.rb

@@ -0,0 +1,51 @@
+class CreateMessageRecipients < ActiveRecord::Migration
+  class Message < ActiveRecord::Base
+    has_many :message_recipients
+  end
+
+  class MessageRecipient < ActiveRecord::Base
+  end
+
+  def up
+    create_table :message_recipients do |t|
+      t.references :message, index: true, null: false
+      t.references :user, null: false
+      t.integer :email_state, default: 0, null: false
+      t.datetime :read_at
+    end
+
+    add_index :message_recipients, [:user_id, :read_at]
+
+    Message.all.each do |m|
+      recipients = YAML.load(m.recipients_ids).map do |r|
+        {
+          message_id: m.id,
+          user_id: r,
+          email_state: m.email_state
+        }
+      end
+      MessageRecipient.create! recipients
+    end
+
+    change_table :messages do |t|
+      t.remove :recipients_ids
+      t.remove :email_state
+    end
+  end
+
+  def down
+    change_table :messages do |t|
+      t.text :recipients_ids
+      t.integer :email_state, default: 0, null: false
+    end
+
+    messages = Message.all.includes(:message_recipients).map do |m|
+      recipients = m.message_recipients.map(&:user_id)
+      m.recipients_ids = recipients.to_yaml
+      m.email_state = m.email_state
+      m.save!
+    end
+
+    drop_table :message_recipients
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20181201000000) do
+ActiveRecord::Schema.define(version: 20181201000100) do
 
   create_table "article_categories", force: :cascade do |t|
     t.string "name",        limit: 255, default: "", null: false
@@ -248,12 +248,20 @@ ActiveRecord::Schema.define(version: 20181201000000) do
 
   add_index "memberships", ["user_id", "group_id"], name: "index_memberships_on_user_id_and_group_id", unique: true, using: :btree
 
+  create_table "message_recipients", force: :cascade do |t|
+    t.integer  "message_id",              null: false
+    t.integer  "user_id",                 null: false
+    t.integer  "email_state", default: 0, null: false
+    t.datetime "read_at"
+  end
+
+  add_index "message_recipients", ["message_id"], name: "index_message_recipients_on_message_id", using: :btree
+  add_index "message_recipients", ["user_id", "read_at"], name: "index_message_recipients_on_user_id_and_read_at", using: :btree
+
   create_table "messages", force: :cascade do |t|
     t.integer  "sender_id",      limit: 4
-    t.text     "recipients_ids", limit: 65535
     t.string   "subject",        limit: 255,                   null: false
     t.text     "body",           limit: 65535
-    t.integer  "email_state",    limit: 4,     default: 0,     null: false
     t.boolean  "private",                      default: false
     t.datetime "created_at"
     t.integer  "reply_to",       limit: 4