Fakey - foreign keys for Rails, in a better way¶ ↑

Before resorting to write yet another foreign key plugin I tried foreign_key_migrations and foreigner, but they have annoying shortcomings. foreign_key_migrations assumes every column ending on _id to be a foreign key and tries to infer the table name, which in my case was not the right one. foreigner doesn’t let you declare foreign key in create_table block, instead you have to call explicitly add_foreign_key(:comments, :posts) after it. Not quite helpful for tables containing a lot of foreign keys.

Both plugins are lousy tested - foreign_key_migrations have no tests at all, and foreigner tests SQL generation only, not the actual migration. Fakey is fully tested by directly inspecting schema in the database. And it supports both MySQL and PostgreSQL.

Example¶ ↑

# Standard usage
create_table :books do |t|
  t.belongs_to :author
end
# => CREATE TABLE "books" ("id" serial primary key, "author_id" integer REFERENCES "authors")

# Table name specified explicitly
create_table :poems do |t|
  t.belongs_to :author, :references => :poets
end
# => CREATE TABLE "poems" ("id" serial primary key, "author_id" integer REFERENCES "poets")

# Column name specified explicitly (if you don't want _id suffix)
create_table :books do |t|
  t.belongs_to :author, :column => :author
end
# => CREATE TABLE "books" ("id" serial primary key, "author" integer REFERENCES "books")

# Non-integer primary key (for those with legacy databases) - this only works in PostgreSQL now!
execute "CREATE TABLE authors( name VARCHAR(255) PRIMARY KEY)"
create_table :books do |t|
  t.belongs_to :author_name, :column => :author_name, :references => :authors, :type => :string
end
# => CREATE TABLE "books" ("id" serial primary key, "author_name" VARCHAR(255) REFERENCES "authors")

# Non-primary key (for those with legacy databases)
create_table :authors do |t|
  t.integer :ssid
end
execute("ALTER TABLE authors ADD UNIQUE(ssid)") # note that add_index doesn't create constraint!
create_table :books do |t|
  t.belongs_to :author_ssid, :column => :author_ssid, :references => :authors, :referenced_column => :ssid
end
# => CREATE TABLE "books" ("id" serial primary key, "author_ssid" integer REFERENCES "authors"(ssid))

# Adding columns to existing - note that you have to use change_table instead of add_column (this works only in PostgreSQL currently)
change_table :atuhors do |t|
  t.belongs_to :author
end

Compatibility¶ ↑

Rails: 2.0+ (tested with 2.0.5, 2.1.2, 2.2.2 and 2.3.4)

Ruby: tested with 1.8.6 and 1.9.1

PostgreSQL 7.0+

MySQL 5.0+

Copyright © 2009 Sava Chankov, released under the MIT license. Thanks to Bryan Evans for database introspection query (taken from drysql gem).