Taking ActiveRecord to the next level contains tips and tricks for using ActiveRecord with enterprise Ruby on Rails Applications. Learn how to import and export multiple records, read off replicas, handle deadlocks, and use temporary tables. Use MySQL functionality such as adding index hints, on duplicate key update, insert select and more.

3. Disclaimer!!!! Premature Optimization

5. ActiveRecord 101 Database Table ff Active Record Model CREATE TABLE `users` ( `id` int(11) NOT NULL auto_increment, `name` varchar(255) default NULL, `password` varchar(255) default NULL, `email` varchar(255) default NULL, `created_at` datetime default NULL, `updated_at` datetime default NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 class User < ActiveRecord::Base end

6. ActiveRecord 101 with Animals! Database Table ff Active Record Model CREATE TABLE `animals` ( `id` int(11) NOT NULL auto_increment, `name` varchar(255) default NULL, `password` varchar(255) default NULL, `email` varchar(255) default NULL, `species_id` int(11) default NULL, `created_at` datetime default NULL, `updated_at` datetime default NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 class Animal < ActiveRecord::Base end

10. Representing Relationships Species name Animal name email password fav_beer updated_at created_at species_id

11. Representing Relationships(DDL) CREATE TABLE `animals` ( `id` int(11) NOT NULL auto_increment, `name` varchar(35) NOT NULL, `email` varchar(40) default NULL, `fav_beer` enum('Guiness','Pabst','Redhook','Chimay') default 'Pabst', `created_at` datetime default NULL, `updated_at` datetime default NULL, `password` varchar(25) character set latin1 collate latin1_bin NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 CREATE TABLE `species` ( `id` int(11) NOT NULL auto_increment, `name` varchar(255), PRIMARY KEY (`id`), ) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8

12. Representing Relationships (AR) class Animal < ActiveRecord::Base belongs_to :species end class Species < ActiveRecord::Base has_many :animals end

13. Representing Relationships (AR) jerry.species SELECT * FROM `species` WHERE (`species`.`id` = 1) species.animals SELECT * FROM `animals` WHERE (`animals`.species_id = 1)

14. Representing Relationships (AR) giraffe = Species.find_by_name 'giraffe' giraffe.animals << jerry SELECT * FROM `species` WHERE (`species`.`name` = 'giraffe' ) LIMIT 1 UPDATE `animals` SET `species_id` = 1, `updated_at` = '2009-03-19 23:15:54' WHERE `id` = 7

16. Migration 101 ruby script/generate scaffold Animal name:string password:string email:string fav_beer:string class CreateAnimals < ActiveRecord::Migration def self.up create_table :animals do |t| t.string :name t.string :password t.string :email t.string :fav_beer t.timestamps end end def self.down drop_table :animals end end

17. Set Limits Default String is VARCHAR(255) create_table :animals do |t| t.string :name, :limit => 35 t.string :password, :limit => 25 t.string :email, :limit => 40 t.string :fav_beer, :limit => 40 t.timestamps end

18. Numeric Type Limits t.integer :mysmallint, :limit => 2 &quot;Smart types&quot; determines numeric type for MySQL 8 bytes bigint 5 to 8 4 bytes int(11) 4, nil, 11 3 bytes mediumint 3 2 bytes smallint 2 1 byte tinyint 1 Column Size Numeric Type :limit

19. Set columns to NOT NULL create_table :animals do |t| t.string :name, :limit => 35, :null => false t.string :password, :limit => 25, :null => false t.string :email, :limit => 40 t.string :fav_beer, :limit => 40 t.timestamps end

20. Set default values create_table :animals do |t| t.string :name, :limit => 35, :null => false t.string :password, :limit => 25, :null => false t.string :email, :limit => 40, :default => nil t.string :fav_beer, :limit => 40 :default => 'Pabst' t.timestamps end

21. Remove unneeded columns create_table :animals do |t| t.string :name, :limit => 35, :null => false t.string :password, :limit => 25, :null => false t.string :email, :limit => 40, :default => nil t.string :fav_beer, :limit => 40 :default => 'Pabst' t.timestamps end

22. Enumerated Column Plugin create_table :animals do |t| t.string :name, :limit => 35, :null => false t.string :password, :limit => 25, :null => false t.string :email, :limit => 40, :default => nil t.enum :fav_beer, :default => 'Pabst' :limit => %w(Chimay Pabst Redhook) t.timestamps end

23. Think about the table parameters create_table :animals, :options => 'ENGINE=MyISAM' do |t| t.string :name, :limit => 35, :null => false t.string :password, :limit => 25, :null => false t.string :email, :limit => 40, :default => nil t.enum :fav_beer, :default => nil :limit => %w(Chimay Pabst Redhook) t.timestamps end

24. Custom DDL create_table :animals do |t| t.string :name, :limit => 35, :null => false t.string :email, :limit => 40, :default => nil t.enum :fav_beer, :default => nil :limit => %w(Chimay Pabst Redhook) t.timestamps end #case sensitive password (encrypted) execute &quot;ALTER TABLE `animals` ADD `password` varchar(25) character set latin1 collate latin1_bin NOT NULL&quot;

25. Create (Unique) Indices create_table :species do |t| t.string :name, :null => false, :limit => 25 end add_index :species, :name, :unique => true, :name => 'uk_species_name'

31. Primary Keys CREATE TABLE `animals` ( `id` int(11) NOT NULL auto_increment, `name` varchar(35) NOT NULL, `email` varchar(40) default NULL, `fav_beer` enum('Guiness','Pabst','Redhook','Chimay') default 'Pabst', `species_id` int(11) default NULL, `created_at` datetime default NULL, `updated_at` datetime default NULL, `password` varchar(25) character set latin1 collate latin1_bin NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 CREATE TABLE `species` ( `id` int(11) NOT NULL auto_increment, `name` varchar(255), PRIMARY KEY (`id`), ) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8

32. Modify the Rails Primary Key Change type with change_column MySQL Migration Optimization Plugin create_table :animals, :primary_key => &quot;special_key&quot;, :primary_column => { :type => :integer, :limit => 2, :precision => :unsigned, :scale => 3 } do |t| end CREATE TABLE `animals` (`special_key` smallint(3) UNSIGNED NOT NULL auto_increment PRIMARY KEY) ENGINE=InnoDB;