Question 1

How do I add a foreign key constraint with Rein in Rails?

Accepted Answer

Use the add_foreign_key_constraint method in your migration, e.g., add_foreign_key_constraint :books, :authors, on_delete: :cascade. The README shows options for indexing and column references.

Question 2

Rein vs ActiveRecord validations: which should I use?

Accepted Answer

Use Rein for database-level integrity that persists even with direct SQL access, ensuring robust data consistency. ActiveRecord validations are better for application logic and user feedback, but can be bypassed.

Question 3

Can Rein be used with Rails 7?

Accepted Answer

Yes, Rein is a Ruby gem compatible with ActiveRecord migrations, so it should work with Rails 7, but always check the gem's latest version for any compatibility notes or updates.

Question 4

How to validate a NOT VALID constraint added with Rein?

Accepted Answer

After adding a constraint with validate: false, use Rails' validate_constraint method (Rails 5.2+) or Rein's validate_table_constraint in a follow-up migration to validate existing rows without locking, as explained in the 'Validate Constraints' section.

Question 5

What databases does Rein support?

Accepted Answer

Rein only supports PostgreSQL because it leverages PostgreSQL-specific features like exclusion constraints and enumerated types. It won't work with MySQL, SQLite, or other databases.

Question 6

How to add a conditional check constraint with Rein?

Accepted Answer

Use the if option in constraints like add_null_constraint or add_inclusion_constraint, e.g., add_null_constraint :books, :due_date, if: "state = 'on_loan'". This applies the constraint only when the condition is met.

Rein

What is Rein?

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