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class ActiveRecord::DatabaseConfigurations

Active Record Database Configurations

ActiveRecord::DatabaseConfigurations returns an array of DatabaseConfig objects that are constructed from the application’s database configuration hash or URL string.

The array of DatabaseConfig objects in an application default to either a HashConfig or UrlConfig. You can retrieve your application’s config by using ActiveRecord::Base.configurations.

If you register a custom handler, objects will be created according to the conditions of the handler. See ::register_db_config_handler for more on registering custom handlers.


[R] configurations

Public class methods

Source code GitHub
# File activerecord/lib/active_record/database_configurations.rb, line 73
def initialize(configurations = {})
  @configurations = build_configs(configurations)

Allows an application to register a custom handler for database configuration objects. This is useful for creating a custom handler that responds to methods your application needs but Active Record doesn’t implement. For example if you are using Vitess, you may want your Vitess configurations to respond to ‘sharded?`. To implement this define the following in an initializer:

ActiveRecord::DatabaseConfigurations.register_db_config_handler do |env_name, name, url, config|
  next unless config.key?(:vitess), name, config)

Note: applications must handle the condition in which custom config should be created in your handler registration otherwise all objects will use the custom handler.

Then define your VitessConfig to respond to the methods your application needs. It is recommended that you inherit from one of the existing database config classes to avoid having to reimplement all methods. Custom config handlers should only implement methods Active Record does not.

class VitessConfig < ActiveRecord::DatabaseConfigurations::UrlConfig
  def sharded?
    configuration_hash.fetch("sharded", false)

For configs that have a :vitess key, a VitessConfig object will be created instead of a UrlConfig.

Source code GitHub
# File activerecord/lib/active_record/database_configurations.rb, line 61
def self.register_db_config_handler(&block)
  db_config_handlers << block

Public instance methods

Alias for: empty?.

Collects the configs for the environment and optionally the specification name passed in. To include replica configurations pass include_hidden: true.

If a name is provided a single DatabaseConfig object will be returned, otherwise an array of DatabaseConfig objects will be returned that corresponds with the environment and type requested.


  • env_name: The environment name. Defaults to nil which will collect configs for all environments.

  • name: The db config name (i.e. primary, animals, etc.). Defaults to nil. If no env_name is specified the config for the default env and the passed name will be returned.

  • config_key: Selects configs that contain a particular key in the configuration hash. Useful for selecting configs that use a custom db config handler or finding configs with hashes that contain a particular key.

  • include_hidden: Determines whether to include replicas and configurations hidden by database_tasks: false in the returned list. Most of the time we’re only iterating over the primary connections (i.e. migrations don’t need to run for the write and read connection). Defaults to false.

Source code GitHub
# File activerecord/lib/active_record/database_configurations.rb, line 98
def configs_for(env_name: nil, name: nil, config_key: nil, include_hidden: false)
  env_name ||= default_env if name
  configs = env_with_configs(env_name)

  unless include_hidden
    configs = do |db_config|

  if config_key
    configs = do |db_config|

  if name
    configs.find do |db_config| == name.to_s

Also aliased as: blank?.

Checks if the application’s configurations are empty.

Source code GitHub
# File activerecord/lib/active_record/database_configurations.rb, line 150
def empty?

Returns a single DatabaseConfig object based on the requested environment.

If the application has multiple databases find_db_config will return the first DatabaseConfig for the environment.

Source code GitHub
# File activerecord/lib/active_record/database_configurations.rb, line 127
def find_db_config(env)
  env = env.to_s
  configurations.find do |db_config|
    db_config.for_current_env? && (db_config.env_name == env || == env)
  end || configurations.find do |db_config|
    db_config.env_name == env


Definition files