db:schema:load vs db:migrate with capistrano

Question

I have a rails app that I'm moving to another server and I figure I should use db:schema:load to create the mysql database because it's recommended. My problem is that I'm using capistrano to deploy and it seems to be defaulting to rake db:migrate instead. Is there a way to change this or is capistrano using db:migrate for a good reason?

Answer 1

Why to use db:schema:load

I find that my own migrations eventually do some shuffling of data (suppose I combine first_name and last_name columns into a full_name column, for instance). As soon as I do any of this, I start using ActiveRecord to sift through database records, and your models eventually make assumptions about certain columns. My "Person" table, for instance, was later given a "position" column by which people are sorted. Earlier migrations now fail to select data, because the "position" column doesn't exist yet.

How to change the default behavior in Capistrano

In conclusion, I believe deploy:cold should use db:schema:load instead of db:migrate. I solved this problem by changing the middle step which Capistrano performs on a cold deploy. For Capistrano v2.5.9, the default task in the library code looks like this.

namespace :deploy do   ...   task :cold do     update     migrate  # This step performs `rake db:migrate`.     start   end   ... end 

I overrode the task in my deploy.rb as follows.

namespace :deploy do   task :cold do       # Overriding the default deploy:cold     update     load_schema       # My own step, replacing migrations.     start   end    task :load_schema, :roles => :app do     run "cd #{current_path}; rake db:schema:load"   end end 

Answer 2

Climbing up on the shoulders of Andres Jaan Tack, Adam Spiers, and Kamiel Wanrooij, I've built the following task to overwrite deploy:cold.

task :cold do   transaction do     update     setup_db  #replacing migrate in original     start   end end  task :setup_db, :roles => :app do   raise RuntimeError.new('db:setup aborted!') unless Capistrano::CLI.ui.ask("About to `rake db:setup`. Are you sure to wipe the entire database (anything other than 'yes' aborts):") == 'yes'   run "cd #{current_path}; bundle exec rake db:setup RAILS_ENV=#{rails_env}" end 

My enhancements here are...

• wrap it in transaction do, so that Capistrano will do a proper rollback after aborting.
• doing db:setup instead of db:schema:load, so that if the database doesn't already exist, it will be created before loading the schema.