Rails - Feb 2009 - config.cache_classes breaks reflect_on_assocation ?

Hi - I have a model with a user-specific has_one relationship,
meaning, my model, Story, has one Vote, but only on a per-user basis.
So, I addressed this issue by adding a has_one relationship:

 has_one :current_user_vote, :class_name => ''Vote'',
:conditions =>
"user_id = #{Story.current_user ? Story.current_user.id : -1}"

And, I added a cattr_accessor, current_user (so now the model Story
has a current user).

And, when the user logs in (or gets logged in by cookie), the method
set_current_user gets called automatically, which looks like this:

def self.set_current_user user
    if user
      holder = user.id
    else
      holder = -1
    end
    reflect_on_association(:current_user_vote).options[:conditions]      
"votes.user_id = #{holder}"
    self.current_user = user
  end

This works fine, unless I enable config.cache_classes, then, the first
user who accesses the site after the server is restarted gets his id
set to current_user, and everyone else afterward gets the first guy''s
user_id set in the association.

So, is there a way to disable only model caching, and cache everything
else? Or, is this a  bug?

Thanks for any help,
Dino
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On 19 Feb 2009, at 20:50, dino d. wrote:
>
> This works fine, unless I enable config.cache_classes, then, the first
> user who accesses the site after the server is restarted gets his id
> set to current_user, and everyone else afterward gets the first
guy''s
> user_id set in the association.
>
> So, is there a way to disable only model caching, and cache everything
> else? Or, is this a  bug?
>
This isn''t a bug - you''re relying on something you should be
relying
on. The reflection builds the sql statement it needs to load the  
association but caches that sql thereafter.
I don''t think there''s a way round this without changing the
way you''re
doing things.

Fred
> Thanks for any help,
> Dino
> >

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thanks fred (i knew you would be the guy to answer this).  so, it
sounds like you cannot ''refresh'' a cached model, and once
it''s cached,
you can''t modify it''s cattr (is this right?) .  hmm... do you
have a
suggestion for a workaround?  I basically have users, stories, and
votes.  users vote on stories.  so, i want load all stories and their
associated votes for a particular user.  this was the only way i could
think of to make a 3 way join.

in the main view of my app, i need to show a batch of stories, with
all the votes for each story, and the current user''s vote for that
story, and i want to do it with a single query.  adding a current user
to the model and the reflect_on does this, and i can''t think of any
other way.

does class caching dramatically improve performance?

without class caching, am i correct to assume that each session has
it''s own model object?

thanks again,
dino

On Feb 19, 6:02 pm, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On 19 Feb 2009, at 20:50, dino d. wrote:
>
>
>
> > This works fine, unless I enable config.cache_classes, then, the first
> > user who accesses the site after the server is restarted gets his id
> > set to current_user, and everyone else afterward gets the first
guy''s
> > user_id set in the association.
>
> > So, is there a way to disable only model caching, and cache everything
> > else? Or, is this a  bug?
>
> This isn''t a bug - you''re relying on something you should
be relying  
> on. The reflection builds the sql statement it needs to load the  
> association but caches that sql thereafter.
> I don''t think there''s a way round this without changing
the way you''re  
> doing things.
>
> Fred
>
> > Thanks for any help,
> > Dino
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dino d. wrote:
> def self.set_current_user user
>     if user
>       holder = user.id
>     else
>       holder = -1
>     end
>     reflect_on_association(:current_user_vote).options[:conditions] >   
"votes.user_id = #{holder}"
>     self.current_user = user
>   end
> 
> This works fine, unless I enable config.cache_classes, then, the first
> user who accesses the site after the server is restarted gets his id
> set to current_user, and everyone else afterward gets the first
guy''s
> user_id set in the association.
Yes, this trick stopped working in 2.2 because the reflection
now caches its conditions SQL.

One workaround is

reflection = reflect_on_association(:current_user_vote)
reflection.options[:conditions] = "votes.user_id = #{holder}"
reflection.instance_eval { @sanitized_conditions = nil }

-- 
Rails Wheels - Find Plugins, List & Sell Plugins - http://railswheels.com

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On 20 Feb 2009, at 00:09, dino d. wrote:
>
> thanks fred (i knew you would be the guy to answer this).  so, it
> sounds like you cannot ''refresh'' a cached model, and once
it''s cached,
> you can''t modify it''s cattr (is this right?) .  hmm... do
you have a
> suggestion for a workaround?  I basically have users, stories, and
> votes.  users vote on stories.  so, i want load all stories and their
> associated votes for a particular user.  this was the only way i could
> think of to make a 3 way join.
>
> in the main view of my app, i need to show a batch of stories, with
> all the votes for each story, and the current user''s vote for that
> story, and i want to do it with a single query.
>  adding a current user
> to the model and the reflect_on does this, and i can''t think of
any
> other way.
It''s not nice but you could have an interpolated condition ie

has_one :blah, :conditions => ''user_id = #{Story.current_user ?  
Story.current_user.id : -1}''

(note the single quotes there).

I think you''d be better off with something that didn''t involve
a class
level variable like this.

something not far removed from

Story.find :all, :include => :votes, :conditions => ["votes.id IS
NULL
OR votes.user_id = ?", foo]

would do the trick (this is a bit messy in that story.votes will now  
return only votes matching the user)
>
>
> does class caching dramatically improve performance?
>
Yes. It''s pretty much the biggest thing (along with caching in the  
sense of fragment caching etc.) that separates development from  
production performance wise.

Fred
> without class caching, am i correct to assume that each session has
> it''s own model object?
>
> thanks again,
> dino
>
> On Feb 19, 6:02 pm, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> wrote:
>> On 19 Feb 2009, at 20:50, dino d. wrote:
>>
>>
>>
>>> This works fine, unless I enable config.cache_classes, then, the  
>>> first
>>> user who accesses the site after the server is restarted gets his
id
>>> set to current_user, and everyone else afterward gets the first  
>>> guy''s
>>> user_id set in the association.
>>
>>> So, is there a way to disable only model caching, and cache  
>>> everything
>>> else? Or, is this a  bug?
>>
>> This isn''t a bug - you''re relying on something you
should be relying
>> on. The reflection builds the sql statement it needs to load the
>> association but caches that sql thereafter.
>> I don''t think there''s a way round this without
changing the way
>> you''re
>> doing things.
>>
>> Fred
>>
>>> Thanks for any help,
>>> Dino
> >

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