I've noticed that because of the query_cache, if you write the value
of an attribute on an ActiveRecord object, the object will continue to
have that "dirty" value even if you ".reload" the object or try and
fetch it again from the DB. Here's an example in a test case. You
could stick this in QueryCacheExpiryTest:
def test_write_attribute
# With our without the query cache shouldn't this behave the same?
task = Task.find(1)
starting = task.starting
task.starting = Time.now
task.reload
assert_equal starting, task.starting
# But this assert will fail
Task.cache do
task = Task.find(1)
task.starting = Time.now
task.reload
assert_equal starting, task.starting
end
end
Should the query cache get cleared when "write_attribute" is called?
I've started working on a patch, couldn't it be as simple as this:
def write_attribute_with_clears_cache(attr_name, value)
if self.class.query_cache
self.class.query_cache.clear_query_cache
end
write_attribute_without_clears_cache(attr_name, value)
end
alias_method_chain :write_attribute, :clears_cache
The query cache stores the returned attributes in a class variable
(Task.query_cache.instance_variable_get(:@query_cache). Modifying an
attribute modifies that same hash, which is why #reload doesn't change
anything.
Please open up a ticket with the failing test patch. I don't think
modifying #write_attribute is the way to go though.
