Rails 每次重启服务器都需要迁移

Question

When deploying my app to heroku , i get some error about migration.

So that I combine all migration, just hold create table file contain all finally property, delete edit table.

Now, everytime restart server(localhost), i have to db:migrate again to everything work.

When i just use db:migrate , the error said: table 'product' already existed' So i have to db:drop first, then db:migrate to make my app work It took me a lot of time. How can I resolve that issue? Here is my migrate status:

up 20190306060445 ********** NO FILE ********** down 20190306060545 Create product up 20190307035103 Create active storage tablesactive storage up 20190308045037 ********** NO FILE ********** up 20190308071304 ********** NO FILE ********** down 20190308072304 Devise create users up 20190308074025 Devise create admins down 20190308082018 Create categories up 20190308083018 ********** NO FILE ********** up 20190311041416 ********** NO FILE ********** up 20190313084429 Create payment up 20190314024236 Create cart up 20190314024911 Create cart product up 20190314035334 Create messages up 20190314145333 Create payment item up 20190314151340 ********** NO FILE ********** up 20190315020606 ********** NO FILE ********** up 20190318073652 Create voucher up 20190319035819 ********** NO FILE ********** up 20190319134032 Contacts up 20190320034249 ********** NO FILE ********** up 20190320062223 ********** NO FILE ********** up 20190325132236 ********** NO FILE ********** up 20190325155829 ********** NO FILE ********** up 20190329095529 ********** NO FILE ********** up 20190329110656 ********** NO FILE ********** up 20190330145000 ********** NO FILE ********** up 20190331162926 ********** NO FILE ********** up 20190408155326 ********** NO FILE ********** up 20190419055934 ********** NO FILE ********** up 20190419060341 ********** NO FILE ********** up 20190502105847 ********** NO FILE ********** up 20190502110019 Add stock up 20190506114910 ********** NO FILE ********** up 20190506115146 ********** NO FILE ********** up 20190506115302 ********** NO FILE ********** up 20190513042021 ********** NO FILE ********** up 20190513050115 ********** NO FILE ********** up 20190514025220 ********** NO FILE ********** up 20190514031046 ********** NO FILE ********** up 20190516010239 Create comment up 20190516020021 ********** NO FILE ********** up 20190517132706 Create notification up 20190524152143 Create brands up 20190527040142 ********** NO FILE ********** up 20190528113143 Add columns devise up 20190528113658 Add columns devise 1 up 20190531125307 Create news up 20190531144908 Create ckeditor assets up 20190601100118 Create news products up 20190602144319 Create type of news up 20190602155208 ********** NO FILE ********** up 20190603062824 ********** NO FILE ********** up 20190606172629 ********** NO FILE ********** up 20190607074100 ********** NO FILE ********** up 20190607122350 ********** NO FILE ********** up 20190607140214 ********** NO FILE ********** up 20190608082804 ********** NO FILE ********** up 20190609051100 Add omniauth to users up 20190611115405 ********** NO FILE ********** up 20190612071933 Create table carousels up 20190612100433 ********** NO FILE ********** up 20190613082404 ********** NO FILE ********** up 20190614131413 ********** NO FILE ********** up 20190615161828 ********** NO FILE ********** up 20190617154212 Create district up 20190617154602 Create province up 20190619140034 Create ward up 20190620134528 ********** NO FILE ********** down 20190620140214 Convert tables to utf8 v1 up 20190622123753 ********** NO FILE **********

Answer 1

In changing all your migrations you've created "new" migrations. rails db:migrate is trying to apply these "new" migrations to an already existing database. (The list of applied migrations is held in the schema_migrations table). We can see all the down migrations are the ones which have not been applied. Including down 20190306060545 Create product .

Since this is a running production database, presumably the product table already exists. When Rails runs migration 20190306060545 Create product which presumably tries to create_table :product it will fail because product already exists.

One way to avoid this is to first check if the table exists in your "create table" migrations. If it does, do nothing.

if table_exists?(:product)
  return
end

To reproduce this in development...

• Check out the original migrations.
• Create a fresh schema from that: rails db:migrate:reset
• Check out your new combined migrations.
• Try to migrate: rails db:migrate