Support for foreign key constraint in Rails

Question

In Ruby on Rails, how to add foreign key constraint in migration?

score 14 · Answer 1 · answered Nov 22 '09 at 08:25

14

Here's a gem-based solution that includes support for adding and removing foreign key constraints, doesn't fail with sqlite, and works correctly with schema.rb files:

http://github.com/matthuhiggins/foreigner

answered Nov 22 '09 at 08:25

Jason Wadsworth

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FYI, `foreigner` doesn't generate foreign keys in `schema.rb` when using SQLite, because SQLite doesn't support foreign keys. – ashes999 Feb 06 '15 at 23:08

score 4 · Answer 2 · answered Apr 09 '10 at 21:24

4

This is an update to the matthuhiggins-foreigner gem: http://github.com/sparkfly/foreigner

Features:

rspec coverage, tested against PostgreSQL 8.3.9 and MySQL 5.0.90
Migration support
schema.rb support

Future versions will include CHECK constraints for PostgreSQL, which is needed to implement multi-table inheritance.

answered Apr 09 '10 at 21:24

Ho-Sheng Hsiao

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Thanks. the foreigner gem does not work well with the change method especially if the table has not been created before. This works great – Sean Feb 08 '12 at 02:06
Your welcomed. Let me know (through github) if you find any bugs. – Ho-Sheng Hsiao Feb 08 '12 at 15:38

score 2 · Accepted Answer · edited Oct 18 '11 at 10:36

2

AFAIK, there isn't any built-in support for that, but there are several plugins that help you with that. You can also add them manually to your migration files, just use the execute method for that, e.g. (sample from Rails API):

  class MakeJoinUnique < ActiveRecord::Migration
    def self.up
      execute "ALTER TABLE `pages_linked_pages` ADD UNIQUE `page_id_linked_page_id` (`page_id`,`linked_page_id`)"
    end

    def self.down
      execute "ALTER TABLE `pages_linked_pages` DROP INDEX `page_id_linked_page_id`"
    end
  end

edited Oct 18 '11 at 10:36

Adam Spiers

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answered Nov 26 '08 at 11:53

Jeroen Heijmans

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Old post, but in case anyone sees this: a unique index is not equivalent to a foreign key constraint, so I believe this code doesn't answer the OP's question. – dsetton Jun 20 '11 at 20:26

score 0 · Answer 4 · answered Aug 16 '11 at 08:05

0

Would it be enough with adding the following, for example with Products and User models?

add_index :products, :user_id

answered Aug 16 '11 at 08:05

noloman

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Adding an index will certainly help with query performance, but it will not make a database enforce foreign key constraints. – Drew Dara-Abrams Aug 03 '12 at 23:25

Support for foreign key constraint in Rails

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