Pablo's blog

A bit of this, a bit of that and a lot about computers

Really resetting the database

When I start coding a Ruby on Rails project, I find myself modifying the migration files over and over. I know this is not the way they were intended to use, but to avoid upfront design, I only ad fields when I need them. If I respected the way migrations were intended I would end up with hundred of migrations the first day and I would waste half my day just creating migrations.

After a project is deployed or a second developer is working on it, I revert to the way migrations are intended and I create a new one every time there’s a change I need in the database.

As migrations are intended to run only once, if you modify them, they won’t get run; and if you force them to run them, they’ll fail, because the database already contains such a table. So I’ve found myself doing this quite often:

rake db:drop && rake db:create && rake db:migrate && rake db:seed && rake db:data

db:data is a task I created to generate some sample data. Good known data that I can use to test the site locally. I’m using Factory Girl to create it, which I also use for the tests so I can re-use as much data creating logic as possible. It’s very good to get to a known state of the project you are developing and to get other developers started right away. I really recommend everyone doing it.

The problem is that I also need to reset my test data, so I end up having this other command and it gets horrible:

RAILS_ENV=test rake db:drop && RAILS_ENV=test rake db:create && RAILS_ENV=test rake db:migrate && RAILS_ENV=test rake db:seed

Note: no db:data this time.

I’ve got tired of re-writing these commands or trying to find them in my bash history, so I decided to write a Ruby task that will do it for me and here it is in case you want to use it too:

namespace :db do
  desc "Crush and burn the database"
  task :hard_reset => :environment do
    File.delete("db/schema.rb")
    Rake::Task["db:drop"].execute
    Rake::Task["db:create"].execute
    Rake::Task["db:migrate"].execute
    Rake::Task["db:seed"].execute
    if !Rails.env.test?
      Rake::Task["db:data"].execute
    end
  end

  desc "Generate sample data for developing"
  task :data => :environment do
    # Create the sample data in here
  end
end

Enjoy!

Update: To delete all records without resetting the whole database, check my post Deleting all records in a Rails project.

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7 thoughts on “Really resetting the database

  1. The article very wonderful and useful.
    Thanks Pablo

  2. take a look at yaml_db http://github.com/adamwiggins/yaml_db/ when you’re first starting an app, it’s kind of annoying to create new migrations when you’re still hammering out all the attrs, imo. i usually don’t add migrations on existing models until the first release and even then, it depends on the project and how large the db is.

    yaml_db adds a couple nice tasks
    rake db:data:dump
    rake db:data:load

  3. btw, great blog!

  4. Pingback: Repost « Sean's Blog

  5. augustin.riedinger on said:

    Pretty old article but it seems to work still! How come nobody else has had the issue of merging migration files while developping since ?
    Thanks anyway!

  6. You can also just redo the last migration (which is what I need most of the time). Really easy rake db:migrate:redo. An alternative is to rollback migrations, rake db:rollback will rollback one step, or rake db:rollback STEP=x will rollback x migrations. And then just do rake db:migrate again. Much easier.

    • Nathan, your advice is fantastic and did exactly what I needed. Great tip for the db:rollback. I had just one problem, rollback only works if you haven’t modified the migration file already. So, I put it back to the way it was before modification (commented out changes), then did the rollback, then redid the migration with the updated file. Worked like a charm. Better than dropping and redoing the whole shebang.

      Pablo, thanks for the pointers in the OP. Will use that sometime if ever needed.

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