Bin/rails generate migration AddPostToComments post:references; That will create a migration with a call to the addreference method instead of addcolumn. Addreference takes a symbol with a table name, and a symbol with the name of a model to add a foreign key for. It'll create a column whose name begins with that model name, and ends in id. Feb 02, 2016 Having primary keys configured for UUIDs via primarykeytype::uuid should make foreign keys in generated migrations UUIDs too. Or at least there should be a foreignkeytype::uuid setting. Such behaviour would be independent from the current state of the database and consistent with the existing generator behaviour for primary keys. Prior to Rails 2.1 the migration number started at 1 and was incremented each time a migration was generated. With multiple developers it was easy for these to clash requiring you to rollback migrations and renumber them. With Rails 2.1+ this is largely avoided by using the creation time of the migration.
Migrations are a convenient way for you to alter your database in a structuredand organized manner. You could edit fragments of SQL by hand but you would thenbe responsible for telling other developers that they need to go and run them.You’d also have to keep track of which changes need to be run against theproduction machines next time you deploy. Generating public and private keys in python file.
Active Record tracks which migrations have already been run so all you have todo is update your source and run rake db:migrate. Active Record will work outwhich migrations should be run. It will also update your db/schema.rb file tomatch the structure of your database.
Rails g nandi:foreignkey payments customers That's just a couple of the things Nandi helps you with: take a look at the project README if you want to know more about using and configuring it. We've been using it in production for a long time now, and have pretty much covered our usage of Postgres - we've written nearly 600 migrations with it. Addforeignkey was originally provided by the Foreigner gem as early as 2012. Rails 4.2 incorporated its methods into the migration DSL out of the box. According to the API docs, it looks like this method does the same thing as t.references. Generators add foreign keys on references If you run a generator such as: ``` rails generate model accounts supplier:references ``` The resulting migration will now add the corresponding foreign key constraint unless the reference was specified to be polymorphic.
Migrations also allow you to describe these transformations using Ruby. Thegreat thing about this is that (like most of Active Record’s functionality) itis database independent: you don’t need to worry about the precise syntax ofCREATE TABLE any more than you worry about variations on SELECT * (you candrop down to raw SQL for database specific features). For example you could useSQLite3 in development, but MySQL in production.
In this guide, you’ll learn all about migrations including: