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Daniel Van den oord

2008-Feb-12 19:00 UTC

has_many through question

I have made 3 tables

+------------+        +----------------+        +------------+
|people      |        |people_campaigns|        |campaigns   |
+------------+        +----------------+        +------------+
|id :int     | <----> |people_id :int  |    /-> |id :int     |
|name :string|        |campaign_id :int| <-/    |name :string|
|etc ...     |        |exported :int   |        |desc :string|
+------------+        +----------------+        +------------+

The people model looks like this

has_many :people_campaigns
has_many :campaigns, :through => :people_campaigns

the other models I left empty because there is no need for me to work
the other way I think

What I want to do is make an export of all people that are in campaign
"x" and are not yet exported. If they are exported then update with
people_campaigns.exported=1

what I did is (except for the fastercsv lines):

people = Person.find(:all)
people.each do |person|
  campaigns = person.campaign
  campaings.each do |campaign|
    if campaign.name == params[:campaignName]
      tester = PeopleCampaign.find(:first,
                                   :conditions => ["person_id=? and
campaign_id=? and isnull(exported)",person.id,campaign.id]
                                   )
      if tester
        #print all to fastercsvlines
        tester.exported = 1
        tester.save
      end
    end
  end
end

This part is out of the top of my head but I don''t like this code and I
think there is a nicer and better (ruby on rails) way to do this ???
especially the part where i lookup the peoplecampaign record for which i
had to add an id (yeah didn''t mention it in the table layout)
-- 
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Thufir

2008-Feb-13 04:59 UTC

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Re: has_many through question

On Feb 12, 11:00 am, Daniel Van den oord <rails-mailing-l...@andreas-
s.net> wrote:> I have made 3 tables
>
> +------------+        +----------------+        +------------+
> |people      |        |people_campaigns|        |campaigns   |
> +------------+        +----------------+        +------------+
> |id :int     | <----> |people_id :int  |    /-> |id :int     |
> |name :string|        |campaign_id :int| <-/    |name :string|
> |etc ...     |        |exported :int   |        |desc :string|
> +------------+        +----------------+        +------------+
>
> The people model looks like this
>
> has_many :people_campaigns
> has_many :campaigns, :through => :people_campaigns
One thing which I notice is that you have two options:

has_many :campaigns, :through => relationships

(choose a better model name than "relationship")

Or:

has_and_belongs to :campaigns_people

with campaigns first.

At least, that''s my understanding.  I don''t think that
there''s
anything technically wrong for a hmt relationship to use
"campaigns_people", but it''s not the convention.



-Thufir
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Daniel Van den oord

2008-Feb-13 06:40 UTC

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Re: has_many through question

My main problem is with the part that it loops twice and does a seperate 
lookup. I am worried that this had major performance problems because 
the Person table will hold 1.2 million records and at least 700.000 
people per campaigns there will be 4 at least this means that the 
people_campaigns table will grow to about 2.8 million records and 
perhaps more

The naming convention I got from the rails wiki but I will look into 
this however this isn''t really the problem
-- 
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Rick DeNatale

2008-Feb-13 15:13 UTC

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Re: has_many through question

On 2/13/08, Daniel Van den oord
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
> My main problem is with the part that it loops twice and does a seperate
> lookup. I am worried that this had major performance problems because
> the Person table will hold 1.2 million records and at least 700.000
> people per campaigns there will be 4 at least this means that the
> people_campaigns table will grow to about 2.8 million records and
> perhaps more
>
> The naming convention I got from the rails wiki but I will look into
> this however this isn''t really the problem
Let''s set this up conventionally:

class Person < ActiveRecord::Base
   has_many :campaigns :through => :campaign_enrollments
   has_many :campaign_enrollments

   # The people table needs at least id as well as any other attributes.
end

class CampaignEnrollment
   belongs_to :person
   belongs_to :campaign
   # The campaign_enrollments table needs at least id, person_id,
campaign_id and exported fields.
end

class Campaign
   has_many :campaign_enrollments
   has_many :people :through => :campaign_enrollments
   # the campaigns table needs at least id field plus other campaign attributes.
end

Now given a campaign

   campaign = Campaign.find(...)

   campaign.campaign_enrollments.find(:all, :include => [:people,
;campaigns] :conditions => ["exported !=?", true]).each do |
campaign_enrollment|
      # whatever exporting does here
     campaign_enrollment.update_attribute(:exported, true)
  end
-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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Thufir

2008-Feb-14 14:56 UTC

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Re: has_many through question

On Feb 13, 3:13 pm, "Rick DeNatale"
<rick.denat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
[...]>    campaign.campaign_enrollments.find(:all, :include => [:people,
> ;campaigns] :conditions => ["exported !=?", true]).each do |
> campaign_enrollment|
>       # whatever exporting does here
>      campaign_enrollment.update_attribute(:exported, true)
>   end[...]

This sort of iteration couldn''t go in the controller, could it?  It
would have to go in the view?


-Thufir
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Daniel Van den oord

2008-Feb-14 15:05 UTC

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Re: has_many through question

If I understood it correctly..
almost eveything that can be in the controller can be done in the view 
(with some exceptions)

however this example is being used for an import and export
the export doesn''t have a view I use fastercsv to generate a csv file 
streaming to the browser..



Thufir wrote:> On Feb 13, 3:13 pm, "Rick DeNatale"
<rick.denat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> [...]
>>    campaign.campaign_enrollments.find(:all, :include => [:people,
>> ;campaigns] :conditions => ["exported !=?", true]).each do
|
>> campaign_enrollment|
>>       # whatever exporting does here
>>      campaign_enrollment.update_attribute(:exported, true)
>>   end
> [...]
> 
> This sort of iteration couldn''t go in the controller, could it? 
It
> would have to go in the view?
> 
> 
> -Thufir
-- 
Posted via http://www.ruby-forum.com/.

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Frederick Cheung

2008-Feb-14 15:15 UTC

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Re: has_many through question

On 13 Feb 2008, at 15:13, Rick DeNatale wrote:
>
> On 2/13/08, Daniel Van den oord
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
> wrote:
>>
>> My main problem is with the part that it loops twice and does a  
>> seperate
>> lookup. I am worried that this had major performance problems because
>> the Person table will hold 1.2 million records and at least 700.000
>> people per campaigns there will be 4 at least this means that the
>> people_campaigns table will grow to about 2.8 million records and
>> perhaps more
>>
>> The naming convention I got from the rails wiki but I will look into
>> this however this isn''t really the problem
>
> Let''s set this up conventionally:
>
> class Person < ActiveRecord::Base
>   has_many :campaigns :through => :campaign_enrollments
>   has_many :campaign_enrollments
>
>   # The people table needs at least id as well as any other  
> attributes.
> end
>
> class CampaignEnrollment
>   belongs_to :person
>   belongs_to :campaign
>   # The campaign_enrollments table needs at least id, person_id,
> campaign_id and exported fields.
> end
>
> class Campaign
>   has_many :campaign_enrollments
>   has_many :people :through => :campaign_enrollments
>   # the campaigns table needs at least id field plus other campaign  
> attributes.
> end
>
> Now given a campaign
>
>   campaign = Campaign.find(...)
>
>   campaign.campaign_enrollments.find(:all, :include => [:people,
> ;campaigns] :conditions => ["exported !=?", true]).each do |
> campaign_enrollment|
>      # whatever exporting does here
>     campaign_enrollment.update_attribute(:exported, true)
>  end
it might be nice to add

has_many :unexported_enrollments, :conditions => ["exported != ?",
true], :class_name => "CampaignEnrollment"
to campaign.

you could then write

campaign.unexported_enrollments.find :all, :include =>  [...] do | 
campaign_enrollment|
...
end

This will do exactly the same thing, but can make things so much more  
readable.


Fred



>
> -- 
> Rick DeNatale
>
> My blog on Ruby
> http://talklikeaduck.denhaven2.com/
>
> >

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Rick DeNatale

2008-Feb-14 16:20 UTC

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Re: has_many through question

On Thu, Feb 14, 2008 at 10:05 AM, Daniel Van den oord
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
>  If I understood it correctly..
>  almost eveything that can be in the controller can be done in the view
>  (with some exceptions)
But it really should be done in the model, with a method used to allow
the controller to trigger it.

Putting too much business logic in a controller is a bad code smell.

Putting too much logic in views is an even bigger bad code smell.

http://weblog.jamisbuck.org/2006/10/18/skinny-controller-fat-model
-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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Rick DeNatale

2008-Feb-14 16:28 UTC

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Re: has_many through question

On Thu, Feb 14, 2008 at 10:15 AM, Frederick Cheung
<frederick.cheung-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>  it might be nice to add
>  has_many :unexported_enrollments, :conditions => ["exported !=
?",
>  true], :class_name => "CampaignEnrollment"
>  to campaign.
or even

  has_many :enrollments, :class_name => "CampaignEnrollment" do
       def unexported
           find(:all, :conditions => ["exported !=>", true]
       end

Which would allow

   campaign.enrollments.unexported.each do | enrollment |
...



   has_many :enrollments>  you could then write
>
>  campaign.unexported_enrollments.find :all, :include =>  [...] do |
>  campaign_enrollment|
>  ...
>  end
>
>  This will do exactly the same thing, but can make things so much more
>  readable.
>
>
>  Fred
>
>
>
>
>
>  >
>  > --
>  > Rick DeNatale
>  >
>  > My blog on Ruby
>  > http://talklikeaduck.denhaven2.com/
>  >
>  > >
>
>
>
>
> >
>


-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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