Question

I’m failing at finding out how to create a database from ActiveRecord if one doesn’t already exist. I’ve looked at this: http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/PostgreSQLAdapter.html#method-i-create_database, but it doesn’t want to play nice, as far as I can tell… I’m not sure what I’m missing here. Is this even possible?

Thanks!

Answer 1

I managed to cobble together this thing that works with both heroku and on my local machine, and will create a database if one doesn’t exist.

# ./lib/db_connect.rb

require 'erb'
require 'uri'
require 'em-synchrony/activerecord'

class DbConnect
  attr_accessor :config
  def initialize
    @db = URI.parse(ENV['DATABASE_URL'] || 'http://localhost')
    if @db.scheme == 'postgres' # This section makes Heroku work
      ActiveRecord::Base.establish_connection(
        :adapter  => @db.scheme == 'postgres' ? 'postgresql' : @db.scheme,
        :host     => @db.host,
        :username => @db.user,
        :password => @db.password,
        :database => @db.path[1..-1],
        :encoding => 'utf8'
      )
    else # And this is for my local environment
      environment = ENV['DATABASE_URL'] ? 'production' : 'development'
      @db = YAML.load(ERB.new(File.read('config/database.yml')).result)[environment]
      ActiveRecord::Base.establish_connection(@db)
      @config = ActiveRecord::Base.connection.pool.spec.config
    end
  end
end

# connect to the database
DbConnect.new

And here’s a Rakefile that uses it.

# ./Rakefile

$: << './lib'
require 'db_connect'

db = DbConnect.new
config = db.config

desc 'create the database'
task :create_db do
  unless ENV['DATABASE_URL'].present?
    ActiveRecord::Base.establish_connection adapter:'postgresql',username:config[:username],password:config[:password], database: 'postgres'
    ActiveRecord::Base.connection.create_database config[:database]
  else
    raise StandardError, "You cannot do this on Heroku!"
  end
end

desc 'create the users table'
task :create_users_table do
  ActiveRecord::Schema.define(:version => 0) do
    create_table "users", :force => true do |t|
      t.string   "first_name"
      t.string   "last_name"
      t.datetime "created_at", :null => false
      t.datetime "updated_at", :null => false
    end
  end
end

Problem solved.