Sometimes, on Mac OS X, programmers accidentally press Option+Space
rather than just Space and don’t see the difference. The problem is
that Option+Space writes a non-breaking space (0XA0) rather than a
normal space (0x20).
This commit removes all the non-breaking spaces inadvertently
introduced in the comments of the code.
At present, ActiveRecord::Delegation compiles delegation methods on a
global basis. The compiled methods apply to all subsequent Relation
instances. This creates several problems:
1) After Post.all.recent has been called, User.all.respond_to?(:recent)
will be true, even if User.all.recent will actually raise an error due
to no User.recent method existing. (See #8080.)
2) Depending on the AR class, the delegation should do different things.
For example, if a Post.zip method exists, then Post.all.zip should call
it. But this will then result in User.zip being called by a subsequent
User.all.zip, even if User.zip does not exist, when in fact
User.all.zip should call User.all.to_a.zip. (There are various
variants of this problem.)
We are creating these compiled delegations in order to avoid method
missing and to avoid repeating logic on each invocation.
One way of handling these issues is to add additional checks in various
places to ensure we're doing the "right thing". However, this makes the
compiled methods signficantly slower. In which case, there's almost no
point in avoiding method_missing at all. (See #8127 for a proposed
solution which takes this approach.)
This is an alternative approach which involves creating a subclass of
ActiveRecord::Relation for each AR class represented. So, with this
patch, Post.all.class != User.all.class. This means that the delegations
are compiled for and only apply to a single AR class. A compiled method
for Post.all will not be invoked from User.all.
This solves the above issues without incurring significant performance
penalties. It's designed to be relatively seamless, however the downside
is a bit of complexity and potentially confusion for a user who thinks
that Post.all and User.all should be instances of the same class.
Benchmark
---------
require 'active_record'
require 'benchmark/ips'
class Post < ActiveRecord::Base
establish_connection adapter: 'sqlite3', database: ':memory:'
connection.create_table :posts
def self.omg
:omg
end
end
relation = Post.all
Benchmark.ips do |r|
r.report('delegation') { relation.omg }
r.report('constructing') { Post.all }
end
Before
------
Calculating -------------------------------------
delegation 4392 i/100ms
constructing 4780 i/100ms
-------------------------------------------------
delegation 144235.9 (±27.7%) i/s - 663192 in 5.038075s
constructing 182015.5 (±21.2%) i/s - 850840 in 5.005364s
After
-----
Calculating -------------------------------------
delegation 6677 i/100ms
constructing 6260 i/100ms
-------------------------------------------------
delegation 166828.2 (±34.2%) i/s - 754501 in 5.001430s
constructing 116575.5 (±18.6%) i/s - 563400 in 5.036690s
Comments
--------
Bear in mind that the standard deviations in the above are huge, so we
can't compare the numbers too directly. However, we can conclude that
Relation construction has become a little slower (as we'd expect), but
not by a huge huge amount, and we can still construct a large number of
Relations quite quickly.
Keying these hashes by klass causes reloadable classes to never get
freed. Thanks to @thedarkone for pointing this out in
the comments on 221571beb6b4bb7437989bdefaf421f993ab6002.
This doesn't seem to make a massive difference to performance.
Benchmark
---------
require 'active_record'
require 'benchmark/ips'
class Post < ActiveRecord::Base
establish_connection adapter: 'sqlite3', database: ':memory:'
end
GC.disable
Benchmark.ips(20) do |r|
r.report { Post.connection }
end
Before
------
Calculating -------------------------------------
5632 i/100ms
-------------------------------------------------
218671.0 (±1.9%) i/s - 4364800 in 19.969401s
After
-----
Calculating -------------------------------------
8743 i/100ms
-------------------------------------------------
206525.9 (±17.8%) i/s - 4039266 in 19.992590s
Allows you to do BaseClass.new(:type => "SubClass") as well as
parent.children.build(:type => "SubClass") or parent.build_child
to initialize an STI subclass. Ensures that the class name is a
valid class and that it is in the ancestors of the super class
that the association is expecting.
Rather than just raising a NoMethodError when copying the config, this
commit adds a warning message until either the rails-observers gem is
installed or the relevant config options are removed.
We are already in the AR namespace, there's no way for it to be
undefined. See the cousin commit 13e72db77063f57c3028a906690d42fb068845bb
Refactor a bit teardown fixtures to avoid two conditionals.
