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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 164
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 212
def connected?
  connection_handler.connected?(connection_specification_name)
end
connected_to(database: nil, role: nil, prevent_writes: false, &blk)

Connects to a database or role (ex writing, reading, or another custom role) for the duration of the block.

If a role is passed, Active Record will look up the connection based on the requested role:

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

ActiveRecord::Base.connected_to(role: :unknown_role) do
  # raises exception due to non-existent role
end
# File activerecord/lib/active_record/connection_handling.rb, line 98
def connected_to(database: nil, role: nil, prevent_writes: false, &blk)
  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
    raise ArgumentError, "connected_to can only accept a `database` or a `role` argument, but not both arguments."
  elsif database
    if database.is_a?(Hash)
      role, database = database.first
      role = role.to_sym
    end

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

    handler.establish_connection(db_config)

    with_handler(role, &blk)
  elsif role
    if role == writing_role
      with_handler(role.to_sym) do
        connection_handler.while_preventing_writes(prevent_writes, &blk)
      end
    else
      with_handler(role.to_sym, &blk)
    end
  else
    raise ArgumentError, "must provide a `database` or a `role`."
  end
end
connected_to?(role:)

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 136
def connected_to?(role:)
  current_role == role.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 175
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 199
def connection_config
  connection_pool.db_config.configuration_hash
end
connection_pool()
# File activerecord/lib/active_record/connection_handling.rb, line 203
def connection_pool
  connection_handler.retrieve_connection_pool(connection_specification_name) || raise(ConnectionNotEstablished)
end
connection_specification_name()

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

# File activerecord/lib/active_record/connection_handling.rb, line 182
def connection_specification_name
  if !defined?(@connection_specification_name) || @connection_specification_name.nil?
    return self == Base ? "primary" : superclass.connection_specification_name
  end
  @connection_specification_name
end
connects_to(database: {})

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

Returns an array of established connections.

# File activerecord/lib/active_record/connection_handling.rb, line 68
def connects_to(database: {})
  connections = []

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

    connections << handler.establish_connection(db_config)
  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 149
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)
  db_config = resolve_config_for_connection(config_or_env)
  connection_handler.establish_connection(db_config)
end
remove_connection(name = nil)
# File activerecord/lib/active_record/connection_handling.rb, line 216
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)
    self.connection_specification_name = nil
  end

  connection_handler.remove_connection(name)
end
retrieve_connection()
# File activerecord/lib/active_record/connection_handling.rb, line 207
def retrieve_connection
  connection_handler.retrieve_connection(connection_specification_name)
end