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

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