If you want to continue using order by random() then just declare it safe by wrapping it in Arel.sql like the deprecation warning suggests: Model.order(Arel.sql(‘random()’)).first # PostgreSQL Model.order(Arel.sql(‘rand()’)).first # MySQL There are lots of ways of selecting a random row and they all have advantages and disadvantages but there are times when you absolutely must … Read more
Here’s a complete answer to this issue, in case people visiting this question are new to Ruby on Rails and having a hard time putting everything together (as I was when I first looked into this). Some parts of the solution take place in your Migrations and some in your Models: Migrations class CreatePrivateMessages < … Read more
Use CREATE SEQUENCE: CREATE SEQUENCE scores_job_id_seq; — = default name for plain a serial Then add a column default to scores.job_id: ALTER TABLE scores ALTER COLUMN job_id SET DEFAULT nextval(‘scores_job_id_seq’); If you want to bind the sequence to the column (so it is deleted when the column is deleted), also run: ALTER SEQUENCE scores_job_id_seq OWNED … Read more
This part of your question: I know we can create it manually in PostgreSQL, but the “magic” with Active Record is that the database can be recreated with all the models. tells me that you’re really looking for a way to integrate PostgreSQL functions with the normal Rails migration process and Rake tasks such as … Read more
Group by offer.id, not by sports.name (or sports.id): SELECT o.* FROM sports s JOIN offers_sports os ON os.sport_id = s.id JOIN offers o ON os.offer_id = o.id WHERE s.name IN (‘Bodyboarding’, ‘Surfing’) GROUP BY o.id — !! HAVING count(*) = 2; Assuming the typical implementation: offer.id and sports.id are defined as primary key. sports.name is … Read more
I believe what you are looking for is assign_attributes. It’s basically the same as update_attributes but it doesn’t save the record: class User < ActiveRecord::Base attr_accessible :name attr_accessible :name, :is_admin, :as => :admin end user = User.new user.assign_attributes({ :name => ‘Josh’, :is_admin => true }) # Raises an ActiveModel::MassAssignmentSecurity::Error user.assign_attributes({ :name => ‘Bob’}) user.name # … Read more
Here’s an example: class RenameOldTableToNewTable < ActiveRecord::Migration def self.up rename_table :old_table_name, :new_table_name end def self.down rename_table :new_table_name, :old_table_name end end I had to go and rename the model declaration file manually. Edit: In Rails 3.1 & 4, ActiveRecord::Migration::CommandRecorder knows how to reverse rename_table migrations, so you can do this: class RenameOldTableToNewTable < ActiveRecord::Migration def change … Read more
For Rails 3, ActiveSupport::Callbacks gives you the necessary control. I was just facing the same challenge in a data integration scenario where normally-desirable-callbacks needed to be brushed aside. You can reset_callbacks en-masse, or use skip_callback to disable judiciously, like this: Vote.skip_callback(:save, :after, :add_points_to_user) ..after which you can operate on Vote instances with :add_points_to_user inhibited
where returns ActiveRecord::Relation Now take a look at find_by implementation: def find_by where(*args).take end As you can see find_by is the same as where but it returns only one record. This method should be used for getting 1 record and where should be used for getting all records with some conditions.
I remember my CompSci professor saying never to use floats for currency. The reason for that is how the IEEE specification defines floats in binary format. Basically, it stores sign, fraction and exponent to represent a Float. It’s like a scientific notation for binary (something like +1.43*10^2). Because of that, it is impossible to store … Read more