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require 'active_support/concern'
require 'thread'
require 'thread_safe'
module ActiveRecord
module Delegation # :nodoc:
extend ActiveSupport::Concern
# This module creates compiled delegation methods dynamically at runtime, which makes
# subsequent calls to that method faster by avoiding method_missing. The delegations
# may vary depending on the klass of a relation, so we create a subclass of Relation
# for each different klass, and the delegations are compiled into that subclass only.
delegate :to_xml, :to_yaml, :length, :collect, :map, :each, :all?, :include?, :to_ary, :to => :to_a
delegate :table_name, :quoted_table_name, :primary_key, :quoted_primary_key,
:connection, :columns_hash, :auto_explain_threshold_in_seconds, :to => :klass
module ClassSpecificRelation
extend ActiveSupport::Concern
included do
@delegation_mutex = Mutex.new
end
module ClassMethods
def name
superclass.name
end
def delegate_to_scoped_klass(method)
@delegation_mutex.synchronize do
return if method_defined?(method)
if method.to_s =~ /\A[a-zA-Z_]\w*[!?]?\z/
module_eval <<-RUBY, __FILE__, __LINE__ + 1
def #{method}(*args, &block)
scoping { @klass.#{method}(*args, &block) }
end
RUBY
else
module_eval <<-RUBY, __FILE__, __LINE__ + 1
def #{method}(*args, &block)
scoping { @klass.send(#{method.inspect}, *args, &block) }
end
RUBY
end
end
end
def delegate(method, opts = {})
@delegation_mutex.synchronize do
return if method_defined?(method)
super
end
end
end
protected
def method_missing(method, *args, &block)
if @klass.respond_to?(method)
self.class.delegate_to_scoped_klass(method)
scoping { @klass.send(method, *args, &block) }
elsif Array.method_defined?(method)
self.class.delegate method, :to => :to_a
to_a.send(method, *args, &block)
elsif arel.respond_to?(method)
self.class.delegate method, :to => :arel
arel.send(method, *args, &block)
else
super
end
end
end
module ClassMethods
@@subclasses = ThreadSafe::Cache.new(:initial_capacity => 2)
def new(klass, *args)
relation = relation_class_for(klass).allocate
relation.__send__(:initialize, klass, *args)
relation
end
# This doesn't have to be thread-safe. relation_class_for guarantees that this will only be
# called exactly once for a given const name.
def const_missing(name)
const_set(name, Class.new(self) { include ClassSpecificRelation })
end
private
# Cache the constants in @@subclasses because looking them up via const_get
# make instantiation significantly slower.
def relation_class_for(klass)
if klass && (klass_name = klass.name)
my_cache = @@subclasses.compute_if_absent(self) { ThreadSafe::Cache.new }
# This hash is keyed by klass.name to avoid memory leaks in development mode
my_cache.compute_if_absent(klass_name) do
# Cache#compute_if_absent guarantees that the block will only executed once for the given klass_name
const_get("#{name.gsub('::', '_')}_#{klass_name.gsub('::', '_')}", false)
end
else
ActiveRecord::Relation
end
end
end
def respond_to?(method, include_private = false)
super || Array.method_defined?(method) ||
@klass.respond_to?(method, include_private) ||
arel.respond_to?(method, include_private)
end
protected
def method_missing(method, *args, &block)
if @klass.respond_to?(method)
scoping { @klass.send(method, *args, &block) }
elsif Array.method_defined?(method)
to_a.send(method, *args, &block)
elsif arel.respond_to?(method)
arel.send(method, *args, &block)
else
super
end
end
end
end
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