Activerecord without Rails

database.yml

# config/database.yml
host: 'localhost'
adapter: 'postgresql'
encoding: utf-8
database: 'test'

Rakefile

require "active_record"

namespace :db do

  db_config       = YAML::load(File.open('config/database.yml'))
  db_config_admin = db_config.merge({'database' => 'postgres', 'schema_search_path' => 'public'})

  desc "Create the database"
  task :create do
    ActiveRecord::Base.establish_connection(db_config_admin)
    ActiveRecord::Base.connection.create_database(db_config["database"])
    puts "Database created."
  end

  desc "Migrate the database"
  task :migrate do
    ActiveRecord::Base.establish_connection(db_config)
    ActiveRecord::Migrator.migrate("db/migrate/")
    Rake::Task["db:schema"].invoke
    puts "Database migrated."
  end

  desc "Drop the database"
  task :drop do
    ActiveRecord::Base.establish_connection(db_config_admin)
    ActiveRecord::Base.connection.drop_database(db_config["database"])
    puts "Database deleted."
  end

  desc "Reset the database"
  task :reset => [:drop, :create, :migrate]

  desc 'Create a db/schema.rb file that is portable against any DB supported by AR'
  task :schema do
    ActiveRecord::Base.establish_connection(db_config)
    require 'active_record/schema_dumper'
    filename = "db/schema.rb"
    File.open(filename, "w:utf-8") do |file|
      ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
    end
  end

end

namespace :g do
  desc "Generate migration"
  task :migration do
    name = ARGV[1] || raise("Specify name: rake g:migration your_migration")
    timestamp = Time.now.strftime("%Y%m%d%H%M%S")
    path = File.expand_path("../db/migrate/#{timestamp}_#{name}.rb", __FILE__)
    migration_class = name.split("_").map(&:capitalize).join

    File.open(path, 'w') do |file|
      file.write <<-EOF
class #{migration_class} < ActiveRecord::Migration

  def self.up
  end

  def self.down
  end

end
      EOF
    end

    puts "Migration #{path} created"
    abort # needed stop other tasks
  end
end

Usage.md

Usage

$ rake db:create # create the db
$ rake db:migrate # run migrations
$ rake db:drop # delete the db
$ rake db:reset # combination of the upper three
$ rake db:schema # creates a schema file of the current database
$ rake g:migration your_migration # generates a new migration file

Rollback (activerecord 5.1)

  desc 'Rollback the database'
  task :rollback, [:steps] do |_task, args|
    steps = (args[:steps] || 1).to_i

    ActiveRecord::Base.establish_connection(DATABASE_CONFIG)
    ActiveRecord::Migrator.rollback(['db/migrate'], steps)

    Rake::Task['db:schema'].invoke
  end

Also refer to Generate migrations outside Rails - Stack Overflow.

Maybe The DatabaseTasks is the best plan. Example

I have made minimal example/setup using Rails migration and active record outside Rails
https://github.com/euclid1990/rails-migration
(Support Rails >= 5.2)
🔢

anybody interested to update this for ActiveRecord 6.0.1?

currently the error I'm getting is: NoMethodError: undefined method migrate' for ActiveRecord::Migrator:Class`

@captainhusaynpinguin yeah it's a little more complicated. you need an instance of ActiveRecord::MigrationContext which needs to be initialized with the path to the migration directory and ActiveRecord::SchemaMigration which will need to have its table created. I would up getting it to work using something like this:

  def schema_migrations
    ActiveRecord::SchemaMigration.tap do |sm|
      sm.create_table
    end
  end

  def migration_context
    ActiveRecord::MigrationContext.new(migration_directory, schema_migrations)
  end

  def migrate
    migration_context.migrate
  end

You could also do the create_table separately before, but I found this to be a little nicer to work with.

Most of this works in the newest version of ActiveRecord, but a few things have to be in for the db:migrate task to work without silently failing. I am using ActiveRecord outside of Rails in this context.

ActiveRecord::Migrator.migrate("db/migrate/") should be replaced with ActiveRecord::Tasks::DatabaseTasks.migrate assuming you are wanting to use the ActiveRecord default directory ('db/migrate'). This fixes NoMethodError: undefined method migrate' for ActiveRecord::Migrator:Class without having to customize anything. It was failing silently before, but this seems to have solved the issue on my end.

I didn't have to mess with MigrationContext at all.

Also, g:migration should have the version number attached to the generated model. You need the version number regardless of the version you are actually using (but it defaults to 4.2). Using activerecord (6.0.2.1) for example...
Before: class #{migration_class} < ActiveRecord::Migration
After: class #{migration_class} < ActiveRecord::Migration[6.0]

https://gist.github.com/Rhoxio/ee9a855088c53d447f2eb888bd9d09a4 if you need a static reference.

The following worked for me when using a db/migrate directory like in rails. ActiveRecord::Tasks::DatabaseTasks is an option too, but the default values have to be changed as it defaults to requiring the Rails object.

def establish_connection
  ActiveRecord::Base.establish_connection(
    {
      adapter: 'postgresql',
      encoding: 'unicode',
      host: 'localhost',
      port: 5432,
      pool: 10,
      username: 'postgres',
      password: 'postgres',
      database: 'your_database_name'
    }
  )
end

def clear_all_connections
  ActiveRecord::Base.clear_all_connections!
end

def generate_schema
  ActiveRecord::Base.connection_pool.with_connection do |connection|
    File.open('db/schema.rb', 'w') do |file|
      ActiveRecord::SchemaDumper.dump(connection, file)
    end
  end
end

def migrate_db
  establish_connection

  ActiveRecord::Base.connection_pool.with_connection do |connection|
    connection.migration_context.migrate
  end

  generate_schema

  clear_all_connections
end

This two fixes made it for me with active record 6.0:

namespace :db do
  # ...
 desc "Migrate the database"
  task :migrate do
    ActiveRecord::Base.establish_connection(db_config)
    ActiveRecord::Base.connection.migration_context.migrate

    Rake::Task["db:schema"].invoke
    puts "Database migrated."
  end

  desc "Rollback the last migration"
  task :rollback do
    step = ENV["STEP"] ? ENV["STEP"].to_i : 1

    ActiveRecord::Base.establish_connection(db_config)
    ActiveRecord::Base.connection.migration_context.rollback(step)

    Rake::Task["db:schema"].invoke
    puts "Database rollback."
  end
  # ...
end

namespace :g do
  desc "Generate migration"
  task :migration do
    name = ARGV[1] || raise("Specify name: rake g:migration your_migration")
    timestamp = Time.now.strftime("%Y%m%d%H%M%S")
    path = File.expand_path("../db/migrate/#{timestamp}_#{name}.rb", __FILE__)
    migration_class = name.split("_").map(&:capitalize).join

    File.open(path, 'w') do |file|
      file.write <<-EOF
class #{migration_class} < ActiveRecord::Migration[6.0]
  def self.up
  end
  def self.down
  end
end
      EOF
    end

    puts "Migration #{path} created"
    abort # needed stop other tasks
  end
end

is it better to load Rake tasks instead? like in this gist:

require 'bundler/setup'

require 'active_record'

include ActiveRecord::Tasks

db_dir = File.expand_path('../db', __FILE__)
config_dir = File.expand_path('../config', __FILE__)

DatabaseTasks.env = 'development'
DatabaseTasks.db_dir = db_dir
DatabaseTasks.database_configuration = YAML.load(File.read(File.join(config_dir, 'database.yml')))
DatabaseTasks.migrations_paths = File.join(db_dir, 'migrate')

task :environment do
  ActiveRecord::Base.establish_connection(
    {
      adapter: 'postgresql',
      encoding: 'unicode',
      host: 'localhost',
      port: 5432,
      pool: 10,
      username: 'postgres',
      password: 'postgres',
      database: 'your_database_name'
    }
  )
  # require_relative './config/environment'
  # ActiveRecord::Base.configurations = DatabaseTasks.database_configuration
  # ActiveRecord::Base.establish_connection DatabaseTasks.env
end

load 'active_record/railties/databases.rake'

@Iaian0 came here to confirm. Loading the default tasks from ActiveRecord works just fine:

load 'active_record/railties/databases.rake'

awesome...thank you for this 👍

It seems to need a Rails constant with ActiveRecord 7.x:

rake db:create
-- create_table(:issues_issues, {:id=>:uuid, :force=>true})
   -> 0.0034s
uninitialized constant primary::Rails

        @root ||= Rails.root
                  ^^^^^

With rails.7.2.1 (activerecord 7.2.0) it works like as with rails6 just fine