edge badge
Methods
C
E
R
Constants
DEFAULT_ENV = -> { RAILS_ENV.call || "default_env" }
 
RAILS_ENV = -> { (Rails.env if defined?(Rails.env)) || ENV["RAILS_ENV"].presence || ENV["RACK_ENV"].presence }
 
Attributes
[W] connection_specification_name
Instance Public methods
clear_query_caches_for_current_thread()

Clears the query cache for all connections associated with the current thread.

# File activerecord/lib/active_record/connection_handling.rb, line 200
def clear_query_caches_for_current_thread
  ActiveRecord::Base.connection_handlers.each_value do |handler|
    handler.connection_pool_list.each do |pool|
      pool.connection.clear_query_cache if pool.active_connection?
    end
  end
end
connected?()

Returns true if Active Record is connected.

# File activerecord/lib/active_record/connection_handling.rb, line 260
def connected?
  connection_handler.connected?(connection_specification_name, shard: current_shard)
end
connected_to(database: nil, role: nil, shard: nil, prevent_writes: false, &blk)

Connects to a role (ex writing, reading or a custom role) and/or shard for the duration of the block. At the end of the block the connection will be returned to the original role / shard.

If only a role is passed, Active Record will look up the connection based on the requested role. If a non-established role is requested an `ActiveRecord::ConnectionNotEstablished` error will be raised:

ActiveRecord::Base.connected_to(role: :writing) do
  Dog.create! # creates dog using dog writing connection
end

ActiveRecord::Base.connected_to(role: :reading) do
  Dog.create! # throws exception because we're on a replica
end

When swapping to a shard, the role must be passed as well. If a non-existent shard is passed, an `ActiveRecord::ConnectionNotEstablished` error will be raised.

When a shard and role is passed, Active Record will first lookup the role, and then look up the connection by shard key.

ActiveRecord::Base.connected_to(role: :reading, shard: :shard_one_replica) do
  Dog.first # finds first Dog record stored on the shard one replica
end

The database kwarg is deprecated and will be removed in 6.2.0 without replacement.

# File activerecord/lib/active_record/connection_handling.rb, line 137
def connected_to(database: nil, role: nil, shard: nil, prevent_writes: false, &blk)
  raise NotImplementedError, "`connected_to` can only be called on ActiveRecord::Base" unless self == Base

  if database
    ActiveSupport::Deprecation.warn("The database key in `connected_to` is deprecated. It will be removed in Rails 6.2.0 without replacement.")
  end

  if database && (role || shard)
    raise ArgumentError, "`connected_to` cannot accept a `database` argument with any other arguments."
  elsif database
    if database.is_a?(Hash)
      role, database = database.first
      role = role.to_sym
    end

    db_config, owner_name = resolve_config_for_connection(database)
    handler = lookup_connection_handler(role)

    handler.establish_connection(db_config, owner_name: owner_name)

    with_handler(role, &blk)
  elsif shard
    unless role
      raise ArgumentError, "`connected_to` cannot accept a `shard` argument without a `role`."
    end

    with_shard(shard, role, prevent_writes, &blk)
  elsif role
    with_role(role, prevent_writes, &blk)
  else
    raise ArgumentError, "must provide a `shard` and/or `role`."
  end
end
connected_to?(role:, shard: ActiveRecord::Base.default_shard)

Returns true if role is the current connected role.

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.connected_to?(role: :writing) #=> true
  ActiveRecord::Base.connected_to?(role: :reading) #=> false
end
# File activerecord/lib/active_record/connection_handling.rb, line 177
def connected_to?(role:, shard: ActiveRecord::Base.default_shard)
  current_role == role.to_sym && current_shard == shard.to_sym
end
connection()

Returns the connection currently associated with the class. This can also be used to “borrow” the connection to do database work unrelated to any of the specific Active Records.

# File activerecord/lib/active_record/connection_handling.rb, line 211
def connection
  retrieve_connection
end
connection_config()

Returns the configuration of the associated connection as a hash:

ActiveRecord::Base.connection_config
# => {pool: 5, timeout: 5000, database: "db/development.sqlite3", adapter: "sqlite3"}

Please use only for reading.

# File activerecord/lib/active_record/connection_handling.rb, line 235
def connection_config
  connection_pool.db_config.configuration_hash
end
connection_db_config()

Returns the db_config object from the associated connection:

ActiveRecord::Base.connection_db_config
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbded10 @env_name="development",
    @name="primary", @config={pool: 5, timeout: 5000, database: "db/development.sqlite3", adapter: "sqlite3"}>

Use only for reading.

# File activerecord/lib/active_record/connection_handling.rb, line 247
def connection_db_config
  connection_pool.db_config
end
connection_pool()
# File activerecord/lib/active_record/connection_handling.rb, line 251
def connection_pool
  connection_handler.retrieve_connection_pool(connection_specification_name, shard: current_shard) || raise(ConnectionNotEstablished)
end
connection_specification_name()

Return the connection specification name from the current class or its parent.

# File activerecord/lib/active_record/connection_handling.rb, line 218
def connection_specification_name
  if !defined?(@connection_specification_name) || @connection_specification_name.nil?
    return self == Base ? Base.name : superclass.connection_specification_name
  end
  @connection_specification_name
end
connects_to(database: {}, shards: {})

Connects a model to the databases specified. The database keyword takes a hash consisting of a role and a database_key.

This will create a connection handler for switching between connections, look up the config hash using the database_key and finally establishes a connection to that config.

class AnimalsModel < ApplicationRecord
  self.abstract_class = true

  connects_to database: { writing: :primary, reading: :primary_replica }
end

connects_to also supports horizontal sharding. The horizontal sharding API also supports read replicas. Connect a model to a list of shards like this:

class AnimalsModel < ApplicationRecord
  self.abstract_class = true

  connects_to shards: {
    default: { writing: :primary, reading: :primary_replica },
    shard_two: { writing: :primary_shard_two, reading: :primary_shard_replica_two }
  }
end

Returns an array of database connections.

# File activerecord/lib/active_record/connection_handling.rb, line 81
def connects_to(database: {}, shards: {})
  raise NotImplementedError, "`connects_to` can only be called on ActiveRecord::Base or abstract classes" unless self == Base || abstract_class?

  if database.present? && shards.present?
    raise ArgumentError, "`connects_to` can only accept a `database` or `shards` argument, but not both arguments."
  end

  connections = []

  database.each do |role, database_key|
    db_config, owner_name = resolve_config_for_connection(database_key)
    handler = lookup_connection_handler(role.to_sym)

    connections << handler.establish_connection(db_config, owner_name: owner_name)
  end

  shards.each do |shard, database_keys|
    database_keys.each do |role, database_key|
      db_config, owner_name = resolve_config_for_connection(database_key)
      handler = lookup_connection_handler(role.to_sym)

      connections << handler.establish_connection(db_config, owner_name: owner_name, shard: shard.to_sym)
    end
  end

  connections
end
current_role()

Returns the symbol representing the current connected role.

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.current_role #=> :writing
end

ActiveRecord::Base.connected_to(role: :reading) do
  ActiveRecord::Base.current_role #=> :reading
end
# File activerecord/lib/active_record/connection_handling.rb, line 190
def current_role
  connection_handlers.key(connection_handler)
end
establish_connection(config_or_env = nil)

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, PostgreSQL, etc):

ActiveRecord::Base.establish_connection(
  adapter:  "mysql2",
  host:     "localhost",
  username: "myuser",
  password: "mypass",
  database: "somedatabase"
)

Example for SQLite database:

ActiveRecord::Base.establish_connection(
  adapter:  "sqlite3",
  database: "path/to/dbfile"
)

Also accepts keys as strings (for parsing from YAML for example):

ActiveRecord::Base.establish_connection(
  "adapter"  => "sqlite3",
  "database" => "path/to/dbfile"
)

Or a URL:

ActiveRecord::Base.establish_connection(
  "postgres://myuser:mypass@localhost/somedatabase"
)

In case ActiveRecord::Base.configurations is set (Rails automatically loads the contents of config/database.yml into it), a symbol can also be given as argument, representing a key in the configuration hash:

ActiveRecord::Base.establish_connection(:production)

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.

# File activerecord/lib/active_record/connection_handling.rb, line 49
def establish_connection(config_or_env = nil)
  config_or_env ||= DEFAULT_ENV.call.to_sym
  db_config, owner_name = resolve_config_for_connection(config_or_env)
  connection_handler.establish_connection(db_config, owner_name: owner_name, shard: current_shard)
end
remove_connection(name = nil)
# File activerecord/lib/active_record/connection_handling.rb, line 264
def remove_connection(name = nil)
  name ||= @connection_specification_name if defined?(@connection_specification_name)
  # if removing a connection that has a pool, we reset the
  # connection_specification_name so it will use the parent
  # pool.
  if connection_handler.retrieve_connection_pool(name, shard: current_shard)
    self.connection_specification_name = nil
  end

  connection_handler.remove_connection_pool(name, shard: current_shard)
end
retrieve_connection()
# File activerecord/lib/active_record/connection_handling.rb, line 255
def retrieve_connection
  connection_handler.retrieve_connection(connection_specification_name, shard: current_shard)
end