# Destroy, dependent and performance

**URL:** <https://www.ruby-forum.com/t/destroy-dependent-and-performance/129238>\
**Category:** Rails\
**Created:** [February 15, 2008, 5:43pm UTC](https://www.ruby-forum.com/t/destroy-dependent-and-performance/129238 "2008-02-15T17:43:18Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![masylum](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@masylum](https://www.ruby-forum.com/u/masylum)\
**Post date:** [February 15, 2008, 5:43pm UTC](https://www.ruby-forum.com/t/destroy-dependent-and-performance/129238/1 "2008-02-15T17:43:18Z")

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Hi!  
This is my first post in this forum. I’m learning RoR for two weeks and  
I’m very interested about how to improve this framework.

I was testing one app I’m working in and I had some problems with  
destroying.

The code is simple (and maybe wrong, as I said i’m just learning!). When  
you destroy a league, you send a message to all the users associated to  
this league.

def destroy  
name = @league.name  
participants = @league.participants  
if @league.destroy  
for participant in participants  
@message = Message.new(:title =\> “blabla”,:text =\> “blabla”,  
:receiver\_id =\> participant.id, :user\_id =\> @user.id)  
@message.save(false)  
end  
flash[:notice] = “League ‘#{name}’ was deleted, you are a criminal!”  
redirect\_to route(’/leagues’)  
else  
flash[:error] = ‘Something went wrong creating this league!’  
redirect\_to route(’/leagues’)  
end  
end

class League \< ActiveRecord::Base  
has\_many :invitations, :dependent =\> :destroy  
has\_many :participants,:through =\> :invitations,:source =\>  
:user,:conditions =\> “accepted == ‘t’”  
end

First of all:  
Leagues and invitations are dependent as you can see in the model. When  
I destroy a League the SQL generated is this:  
[DEBUG] Invitation Load SELECT \* FROM invitations WHERE  
(invitations.league\_id = 1)  
[DEBUG] Invitation Destroy DELETE FROM invitations WHERE “id” = 12e  
[DEBUG] Invitation Destroy DELETE FROM invitations WHERE “id” = 15

If you have 100 invitations, you have to do 101 db calls?  
I think it will be better to just make a  
DELETE FROM invitations WHERE league\_id = 1

Maybe i’m not using :dependent =\>:destroy in the correct way…

The second problem i have is about creating messages. When i call to  
league.destroy it deletes all invitations and then my participants  
variable is empty. Do you know what can i do?

Thank’s in advance and sorry for my english! I’m trying to learn it as  
well.

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<div class="post-metadata">

**Author:** ![masylum](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@masylum](https://www.ruby-forum.com/u/masylum)\
**Post date:** [February 16, 2008, 6:32pm UTC](https://www.ruby-forum.com/t/destroy-dependent-and-performance/129238/2 "2008-02-16T18:32:19Z")

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Have a closer look at the docs for has\_many (http://  
[api.rubyonrails.org/classes/ActiveRecord/Associations/](http://api.rubyonrails.org/classes/ActiveRecord/Associations/)  
ClassMethods.html#M001103). If you want to get rid of all the  
invitations without reading them into memory you want to  
use :dependent=\>:delete\_all. :destroy should be used if you need to  
do additional work in each associated object (e.g., they have  
dependents as well) as it instantiates each associated object and  
invokes destroy on it. :delete\_all just deletes them at the db-level  
without instantiating.

My guess as to why your participants local variable is empty is that  
the method you’re using simply creates an object that points to the  
‘participants’ association proxy on @league (it looks like an array,  
but it’s really a proxy object). To get an array that won’t disappear  
when the invitations are destroy you could probably do this…

participants = @league.participants.find(:all)

or

participants = @league.participants.dup

On Feb 15, 11:43 am, Pau R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

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<div class="post-metadata">

**Author:** ![masylum](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@masylum](https://www.ruby-forum.com/u/masylum)\
**Post date:** [February 18, 2008, 2:29am UTC](https://www.ruby-forum.com/t/destroy-dependent-and-performance/129238/3 "2008-02-18T02:29:14Z")

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Thank’s man! It’s nice to have a place like this forum with people like  
you.

I didn’t understood the :delete\_all description in the docs but now i  
undertand how it works.

The second tip works as well. Great!

Thank’s!

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<div class="post-metadata">

**Author:** ![masylum](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@masylum](https://www.ruby-forum.com/u/masylum)\
**Post date:** [February 18, 2008, 8:01pm UTC](https://www.ruby-forum.com/t/destroy-dependent-and-performance/129238/4 "2008-02-18T20:01:02Z")

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Congrats!

On Feb 17, 8:29 pm, Pau R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)