1

I'm using RoR5 with PostgreSQL. I have a table with a column status. Which is of a type integer and holds three values 0, 1, 2. Those values represent three statuses allowed, not_allowed and no_tests.

I'm gonna change the logic. I want to convert two statuses allowed and not_allowed into boolean. Then I'll create a separate column for the no_tests.

Right now I have this accordance: enum status: %i[allowed not_allowed no_tests].

How should I write a migration to have allowed as true and both not_allowed and no_tests as false in the changed column?

Chetan Datta
  • 447
  • 9
  • 19
ik00ma
  • 422
  • 6
  • 24
  • @user1023110 After reading this article https://robots.thoughtbot.com/data-migrations-in-rails I think I will stick to your approach. It really smells bad to manipulate data in migration. Please answer and I will accept the solution. – ik00ma Dec 28 '17 at 18:31

2 Answers2

1

Actually this is two separate operations (change table structure, convert existing data), only one of would typically be done in a migration. If I were you I would first run a migration to add the new status column, and then do an update either in sql if you have easy access to the postgres console or at the rails console to recode the existing data in your new column. After you've recoded the data you can drop the old columns in another migration.

GGizmos
  • 3,443
  • 4
  • 27
  • 72
0

I think you will need some stuff in up method within migration.

def up
  add_column :table_name, :status2, :boolean
  Loop on each element of model check for status and update status2
  remove_column :table_name, :status
  rename_column :table_name, :status2, :status
end

You can also go with case statement in update here It will help. You can put your query in migration as well something similar to here.

You can also do one more thing like :
1. Make migration to add new column.
2. Make rake task to populate data.
3. Make one more migration to delete old column and rename newly added column.

Update : For better understanding on migration do read this article.

Manishh
  • 1,444
  • 13
  • 23