# :include doesn't work with belongs\_to

**URL:** <https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800>\
**Category:** Rails\
**Created:** [December 1, 2007, 1:00am UTC](https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800 "2007-12-01T01:00:43Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Mozmonkey](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/4491bb/32.png) [@Mozmonkey](https://www.ruby-forum.com/u/Mozmonkey)\
**Post date:** [December 1, 2007, 1:00am UTC](https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800/1 "2007-12-01T01:00:43Z")

</div>

I’m having issues getting :include to eagerly load data in a  
“belongs\_to” association. Here’s the breakdown:

Users have friends and an avatar image. If I am loading all the  
user’s friends I want to also eagerly load the images for those users  
in the same SQL query – instead of 1 query per friend, which adds up  
quickly. Here are my models:

Image  
belongs\_to :imageable, :polymorphic =\> true

User  
has\_many :images, :as =\> :imageable  
has\_many :friends, :include =\> :user,

Friend  
# The user  
belongs\_to :owner\_user,  
:class\_name =\> “User”,  
:foreign\_key =\>“user\_id”,

```
# The friend
belongs_to :user,
                 :class_name => "User",
                 :foreign_key => "friend_id",
                 :include => :images

```

As you can see I use :include on User#friends for “user” and then on  
Friend#user for “images”. My thinking is, when accessing  
User#friends, rails will eagerly load the User object for each friend  
and all the images for that user.

friend -\> user -\> images

Currently the first part works (friend -\> user), but it does not query  
for the images at the same time. So when I list all a user’s friends  
with their avatars I get a lot of SQL queries.

What am I doing wrong? How can I optimize this?

---

<div class="post-metadata">

**Author:** ![Mozmonkey](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/4491bb/32.png) [@Mozmonkey](https://www.ruby-forum.com/u/Mozmonkey)\
**Post date:** [December 1, 2007, 3:41am UTC](https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800/2 "2007-12-01T03:41:09Z")

</div>

Mozmonkey wrote:

> I’m having issues getting :include to eagerly load data in a  
> “belongs\_to” association. Here’s the breakdown:

I believe there is a known bug with eager loading and belongs\_to. I just  
can’t find the ticket in trac.

–  
Josh S.  
[http://blog.hasmanythrough.com](http://blog.hasmanythrough.com)

---

<div class="post-metadata">

**Author:** ![Mozmonkey](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/4491bb/32.png) [@Mozmonkey](https://www.ruby-forum.com/u/Mozmonkey)\
**Post date:** [December 1, 2007, 8:02am UTC](https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800/3 "2007-12-01T08:02:11Z")

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Is there any work around that you can think of?

Thanks!  
Jeremy

---

<div class="post-metadata">

**Author:** ![Mozmonkey](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/4491bb/32.png) [@Mozmonkey](https://www.ruby-forum.com/u/Mozmonkey)\
**Post date:** [December 1, 2007, 1:49pm UTC](https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800/4 "2007-12-01T13:49:47Z")

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I thought the known problem was the other way round?

ie if I’m loading some Images and i want to include :imageable then  
we’re stuck (because we don;t know which tables to join on, and even  
if you do it would probably be rather ineffecient. (There is a patch  
out there (blowing my own horn for a second:  
[http://dev.rubyonrails.org/ticket/9640](http://dev.rubyonrails.org/ticket/9640)),  
which does address this (although mainly as a side effect of  
completely replacing :include)). You can get this by hand: give the  
array of things, find the distinct types and do one query per type.

In this case you do get a warning about not being able to :include the  
polymorphic association. I thought the other way round was ok though.  
The code in associations.rb certainly looks like it’s trying to handle  
it.

Fred

---

<div class="post-metadata">

**Author:** ![Mozmonkey](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/4491bb/32.png) [@Mozmonkey](https://www.ruby-forum.com/u/Mozmonkey)\
**Post date:** [December 1, 2007, 8:37pm UTC](https://www.ruby-forum.com/t/include-doesnt-work-with-belongs-to/121800/5 "2007-12-01T20:37:31Z")

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OK, so using polymorphic is what breaks this? So should is it more  
efficient to have different Models for different image types? I’ll  
also go checkout your solution right now.