From 07723c23a7dc570beae73c074ad37227e3e8a06e Mon Sep 17 00:00:00 2001 From: Sean Griffin Date: Mon, 28 Sep 2015 17:12:28 -0400 Subject: Further encapsulate dirty checking on `Attribute` We can skip the allocation of a full `AttributeSet` by changing the semantics of how we structure things. Instead of comparing two separate `AttributeSet` objects, and `Attribute` is now a singly linked list of every change that has happened to it. Since the attribute objects are immutable, to apply the changes we simply need to copy the head of the list. It's worth noting that this causes one subtle change in the behavior of AR. When a record is saved successfully, the `before_type_cast` version of everything will be what was sent to the database. I honestly think these semantics make more sense, as we could have just as easily had the DB do `RETURNING *` and updated the record with those if we had things like timestamps implemented at the DB layer. This brings our performance closer to 4.2, but we're still not quite there. --- activerecord/test/cases/attribute_test.rb | 39 ++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) (limited to 'activerecord/test/cases/attribute_test.rb') diff --git a/activerecord/test/cases/attribute_test.rb b/activerecord/test/cases/attribute_test.rb index 0f216b7a13..a24a4fc6a4 100644 --- a/activerecord/test/cases/attribute_test.rb +++ b/activerecord/test/cases/attribute_test.rb @@ -182,12 +182,49 @@ module ActiveRecord assert attribute.has_been_read? end + test "an attribute is not changed if it hasn't been assigned or mutated" do + attribute = Attribute.from_database(:foo, 1, Type::Value.new) + + refute attribute.changed? + end + + test "an attribute is changed if it's been assigned a new value" do + attribute = Attribute.from_database(:foo, 1, Type::Value.new) + changed = attribute.with_value_from_user(2) + + assert changed.changed? + end + + test "an attribute is not changed if it's assigned the same value" do + attribute = Attribute.from_database(:foo, 1, Type::Value.new) + unchanged = attribute.with_value_from_user(1) + + refute unchanged.changed? + end + test "an attribute can not be mutated if it has not been read, and skips expensive calculations" do type_which_raises_from_all_methods = Object.new attribute = Attribute.from_database(:foo, "bar", type_which_raises_from_all_methods) - assert_not attribute.changed_in_place_from?("bar") + assert_not attribute.changed_in_place? + end + + test "an attribute is changed if it has been mutated" do + attribute = Attribute.from_database(:foo, "bar", Type::String.new) + attribute.value << "!" + + assert attribute.changed_in_place? + assert attribute.changed? + end + + test "an attribute can forget its changes" do + attribute = Attribute.from_database(:foo, "bar", Type::String.new) + changed = attribute.with_value_from_user("foo") + forgotten = changed.forgetting_assignment + + assert changed.changed? # sanity check + refute forgotten.changed? end test "with_value_from_user validates the value" do -- cgit v1.2.3