Automatic loading of parent association weirdness?

rubyonrails-talk
1

Hi there,

I'm experiencing some weird behavior with automatic loading of parent associations in ActiveRecord using Rails 2.1.

Let's take this simple model:

<snip>

class Contact < ActiveRecord::Base   has_many :assets end

class Asset < ActiveRecord::Base   belongs_to :contact end

</snip>

And here follows a console/development.log transcript:

<snip>

a = Asset.find(:first, :include => {:contact => :assets})

Asset Load (0.000399) SELECT * FROM `assets` LIMIT 1 Contact Load (0.000300) SELECT * FROM `contacts` WHERE (`contacts`.id IN ('1')) Asset Load (0.009318) SELECT `assets`.* FROM `assets` WHERE (`assets`.contact_id IN (1))

(looks alright to me)

c = a.contact

(This yields no query, as expected)

f = c.assets.first

(This yields no query, as expected)

f.contact

Contact Load (0.000408) SELECT * FROM `contacts` WHERE (`contacts`.`id` = 1)

</snip>

Now why isn't this asset's contact record already associated to the existing contact instance?

I've been using Rails for years and it's the very first time I notice such a behavior. It has always occured to me that, when invoking parent.association, all records in association had their parent already set to an existing instance, without having to hit the database.

Any idea on this?

Greets,

Xavier

2

Hi there,

Now why isn't this asset's contact record already associated to the existing contact instance?

I've been using Rails for years and it's the very first time I notice such a behavior. It has always occured to me that, when invoking parent.association, all records in association had their parent already set to an existing instance, without having to hit the database.

It's always been like this (:include is a red herring here, even
without eager loading in the picture, if you do

x = parent.child #=> 1 query, loads child x.parent #=> 1 query, loads parent again)

This is far from ideal but it's nothing new

Fred

3

This is far from ideal but it's nothing new

Wow, I am so totally baffled.

I'm still wondering how I managed to never notice this, I've always taken the presence of the parent for granted when loading members of an association... probably because this lack doesn't make a whole lot of sense, does it? :wink:

Thanks for the reality check anyway.

Cheers

Xavier