db:schema:load vs db:migrate with capistrano

Question

Hi, 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

To create the new database use rake db:create, also if db:migrate is working already for you, then there isn't really a reason to change to db:schema:load. db:schema:load is a faster, but unless you are running thousands of migrations the actual wall clock time difference is minimal.

Answer 2

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