DEV: Migrate Chat::NotificationMention#notification_id to bigint (#28571)

`Notification#id` was migrated to `bigint` in 799a45a291

plugins/chat/app/models/chat/mention_notification.rb

@@ -4,6 +4,10 @@ module Chat
   class MentionNotification < ActiveRecord::Base
     self.table_name = "chat_mention_notifications"
 
+    self.ignored_columns = [
+      :old_notification_id, # TODO remove once this column is removed. Migration to drop the column has not been written.
+    ]
+
     belongs_to :chat_mention, class_name: "Chat::Mention"
     belongs_to :notification, dependent: :destroy
   end
@@ -13,8 +17,8 @@ end
 #
 # Table name: chat_mention_notifications
 #
-#  chat_mention_id    :integer    not null
-#  notification_id    :integer    not null
+#  chat_mention_id :integer          not null
+#  notification_id :bigint           not null
 #
 # Indexes
 #

plugins/chat/db/migrate/20240827040131_add_new_notification_id_to_chat_mention_notifications.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+class AddNewNotificationIdToChatMentionNotifications < ActiveRecord::Migration[7.1]
+  def up
+    # Create new column
+    execute "ALTER TABLE chat_mention_notifications ADD COLUMN new_notification_id BIGINT NOT NULL DEFAULT(0)"
+
+    # Mirror new `notification_id` values to `new_notification_id`
+    execute(<<~SQL)
+      CREATE FUNCTION mirror_chat_mention_notifications_notification_id()
+      RETURNS trigger AS
+      $$
+      BEGIN
+        NEW.new_notification_id = NEW.notification_id;
+        RETURN NEW;
+      END;
+      $$
+      LANGUAGE plpgsql
+    SQL
+
+    execute(<<~SQL)
+      CREATE TRIGGER chat_mention_notifications_new_notification_id_trigger BEFORE INSERT ON chat_mention_notifications
+      FOR EACH ROW EXECUTE PROCEDURE mirror_chat_mention_notifications_notification_id()
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

plugins/chat/db/migrate/20240827040550_copy_chat_mention_notifications_notification_id_values.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+class CopyChatMentionNotificationsNotificationIdValues < ActiveRecord::Migration[7.1]
+  disable_ddl_transaction!
+
+  def up
+    min_id, max_id =
+      execute("SELECT MIN(notification_id), MAX(notification_id) FROM chat_mention_notifications")[
+        0
+      ].values
+    batch_size = 10_000
+
+    (min_id..max_id).step(batch_size) { |start_id| execute <<~SQL.squish } if min_id && max_id
+        UPDATE chat_mention_notifications
+        SET new_notification_id = notification_id
+        WHERE notification_id >= #{start_id} AND notification_id < #{start_id + batch_size} AND new_notification_id != notification_id
+      SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

plugins/chat/db/migrate/20240827040810_copy_chat_mention_notifications_notification_id_indexes.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+class CopyChatMentionNotificationsNotificationIdIndexes < ActiveRecord::Migration[7.1]
+  disable_ddl_transaction!
+
+  def up
+    execute "DROP INDEX #{Rails.env.test? ? "" : "CONCURRENTLY "} IF EXISTS index_chat_mention_notifications_on_new_notification_id"
+    execute "CREATE UNIQUE INDEX #{Rails.env.test? ? "" : "CONCURRENTLY "} index_chat_mention_notifications_on_new_notification_id ON chat_mention_notifications (new_notification_id)"
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

plugins/chat/db/migrate/20240827040811_swap_bigint_chat_mention_notifications_notification_id.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+class SwapBigintChatMentionNotificationsNotificationId < ActiveRecord::Migration[7.1]
+  def up
+    # Necessary to rename and drop trigger/function
+    Migration::SafeMigrate.disable!
+
+    # Drop trigger and function used to replicate new values
+    execute "DROP TRIGGER chat_mention_notifications_new_notification_id_trigger ON chat_mention_notifications"
+    execute "DROP FUNCTION mirror_chat_mention_notifications_notification_id()"
+
+    # Swap columns
+    execute "ALTER TABLE chat_mention_notifications RENAME COLUMN notification_id TO old_notification_id"
+    execute "ALTER TABLE chat_mention_notifications RENAME COLUMN new_notification_id TO notification_id"
+
+    # Drop old indexes
+    execute "DROP INDEX index_chat_mention_notifications_on_notification_id"
+    execute "ALTER INDEX index_chat_mention_notifications_on_new_notification_id RENAME TO index_chat_mention_notifications_on_notification_id"
+
+    execute "ALTER TABLE chat_mention_notifications ALTER COLUMN old_notification_id DROP NOT NULL"
+    execute "ALTER TABLE chat_mention_notifications ALTER COLUMN notification_id DROP DEFAULT"
+
+    # Keep old column and mark it as read only
+    Migration::ColumnDropper.mark_readonly(:chat_mention_notifications, :old_notification_id)
+  ensure
+    Migration::SafeMigrate.enable!
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end