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Wildtangent

2008-Jan-10 18:30 UTC

has_many/belongs_to relationship that doesn''t use id

Hi,

Banging by head against a wall here, and i''m sure this is easy

I have a table called channel_statistics and one called installations

in both there is a column called node_identifier

I want to be able to do

ChannelStatistic.find(:all, :include => [:installations]) as this has
a lot of data in it I want to eager load

so i have tried

class ChannelStatistic < ActiveRecord::Base

  belongs_to :installation, :foreign_key =>
''node_identifier''

 ...
end

class Installation < ActiveRecord::Base

   has_many :channel_statistics, :foreign_key =>
''node_identifier''

....
end

but to no avail.

It always performs the "LEFT OUTER JOIN on installations.id
channel_statistics.node_identifier"

What I want it to do is "LEFT OUTER JOIN on
installations.node_identifier = channel_statistics.node_identifier"


Guess they might not be able to handle this but it seems unlikely
somehow!
Possibility that with_scope might help but I have never got that
working how I want either


Please help!!

Thanks

Joe
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Ryan Bigg

2008-Jan-10 20:42 UTC

head link

Re: has_many/belongs_to relationship that doesn''t use id

So you want to define all channel statistics that belong to an installation
and all installations that belong to a channel statistic? This sounds like a
has and belongs to many, or has_many through problem :)

On Jan 11, 2008 5:00 AM, Wildtangent
<wildtangent-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> Hi,
>
> Banging by head against a wall here, and i''m sure this is easy
>
> I have a table called channel_statistics and one called installations
>
> in both there is a column called node_identifier
>
> I want to be able to do
>
> ChannelStatistic.find(:all, :include => [:installations]) as this has
> a lot of data in it I want to eager load
>
> so i have tried
>
> class ChannelStatistic < ActiveRecord::Base
>
>  belongs_to :installation, :foreign_key =>
''node_identifier''
>
>  ...
> end
>
> class Installation < ActiveRecord::Base
>
>   has_many :channel_statistics, :foreign_key =>
''node_identifier''
>
> ....
> end
>
> but to no avail.
>
> It always performs the "LEFT OUTER JOIN on installations.id >
channel_statistics.node_identifier"
>
> What I want it to do is "LEFT OUTER JOIN on
> installations.node_identifier = channel_statistics.node_identifier"
>
>
> Guess they might not be able to handle this but it seems unlikely
> somehow!
> Possibility that with_scope might help but I have never got that
> working how I want either
>
>
> Please help!!
>
> Thanks
>
> Joe
> >
>

-- 
Ryan Bigg
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.

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Wildtangent

2008-Jan-11 10:04 UTC

head link

Re: has_many/belongs_to relationship that doesn''t use id

The association just needs to work with both keys being named
node_identifier
It can''t use the normal rails _id convention because the stats get
dumped by a separate app and i am not able to perform a lookup on the
node_identifier to find the installation_id before each stats update
(would create too much db activity)

So the question is simply, how do i override rails''s usually magic
presets and create an assocation between the two tables which uses the
node_identifier column in both tables as the join.

There is only ever one installation per channel statistic so it is not
a HABTM problem

THanks again!


On Jan 10, 8:42 pm, "Ryan Bigg"
<radarliste...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> So you want to define all channel statistics that belong to an installation
> and all installations that belong to a channel statistic? This sounds like
a
> has and belongs to many, or has_many through problem :)
>
> On Jan 11, 2008 5:00 AM, Wildtangent
<wildtang...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
>
>
>
> > Hi,
>
> > Banging by head against a wall here, and i''m sure this is
easy
>
> > I have a table called channel_statistics and one called installations
>
> > in both there is a column called node_identifier
>
> > I want to be able to do
>
> > ChannelStatistic.find(:all, :include => [:installations]) as this
has
> > a lot of data in it I want to eager load
>
> > so i have tried
>
> > class ChannelStatistic < ActiveRecord::Base
>
> >  belongs_to :installation, :foreign_key =>
''node_identifier''
>
> >  ...
> > end
>
> > class Installation < ActiveRecord::Base
>
> >   has_many :channel_statistics, :foreign_key =>
''node_identifier''
>
> > ....
> > end
>
> > but to no avail.
>
> > It always performs the "LEFT OUTER JOIN on installations.id >
> channel_statistics.node_identifier"
>
> > What I want it to do is "LEFT OUTER JOIN on
> > installations.node_identifier =
channel_statistics.node_identifier"
>
> > Guess they might not be able to handle this but it seems unlikely
> > somehow!
> > Possibility that with_scope might help but I have never got that
> > working how I want either
>
> > Please help!!
>
> > Thanks
>
> > Joe
>
> --
> Ryan Bigghttp://www.frozenplague.net
> Feel free to add me to MSN and/or GTalk as this email.--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
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To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
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Wildtangent

2008-Jan-15 12:43 UTC

head link

Re: has_many/belongs_to relationship that doesn''t use id

I''m going to answer my own question because I''m sure
I''m not alone
with this problem

The solution I came up with was to subclass the main ActiveRecord
model and override the primary key and relationships in there

e.g.

(Main Model Class)
class Installation < ActiveRecord::Base
    #...some normal relationships here
end

(subclassed)
class InstallationStatistic < Installation

    set_primary_key ''node_identifier''

    has_many :channel_statistics, :foreign_key =>
''node_identifier''

   def save
       do_not_save_and_warn
   end
   alias_method :save!, :save
   alias_method :create, :save
   alias_method :create!, :save
   alias_method :<<, :save

   private
   def do_not_save_and_warn
        logger.warn("Can''t save with this model for association
only.
Instantiate Installation instead.")
   end

end

(association)
class ChannelStatistic < ActiveRecord::Base
     belongs_to :installation, :class_name =>
''InstallationStatistic, :foreign_key =>
''node_identifier''
end


This seems to allow me to maintain my relationships with Installation
and its other relationships, while creating a new one based on a
different primary key. I have overridden the save methods so that we
don''t mess up the installation table or try and create a subclassed
entry.

Now i can do
>> channel_statistic = ChannelStatistic.find(:first)
>> channel_statistic.installation<#IInstallationStatistic id: 54, node_identifier: blah, :user_id:
75>>> channel_statistic.installation.user<#User id: 75, login: blah>

Great!!

On Jan 11, 10:04 am, Wildtangent
<wildtang...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> The association just needs to work with both keys being named
> node_identifier
> It can''t use the normal rails _id convention because the stats get
> dumped by a separate app and i am not able to perform a lookup on the
> node_identifier to find the installation_id before each stats update
> (would create too much db activity)
>
> So the question is simply, how do i override rails''s usually magic
> presets and create an assocation between the two tables which uses the
> node_identifier column in both tables as the join.
>
> There is only ever one installation per channel statistic so it is not
> a HABTM problem
>
> THanks again!
>
> On Jan 10, 8:42 pm, "Ryan Bigg"
<radarliste...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > So you want to define all channel statistics that belong to an
installation
> > and all installations that belong to a channel statistic? This sounds
like a
> > has and belongs to many, or has_many through problem :)
>
> > On Jan 11, 2008 5:00 AM, Wildtangent
<wildtang...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > Hi,
>
> > > Banging by head against a wall here, and i''m sure this
is easy
>
> > > I have a table called channel_statistics and one called
installations
>
> > > in both there is a column called node_identifier
>
> > > I want to be able to do
>
> > >ChannelStatistic.find(:all, :include => [:installations]) as
this has
> > > a lot of data in it I want to eager load
>
> > > so i have tried
>
> > > classChannelStatistic< ActiveRecord::Base
>
> > >  belongs_to :installation, :foreign_key =>
''node_identifier''
>
> > >  ...
> > > end
>
> > > class Installation < ActiveRecord::Base
>
> > >   has_many :channel_statistics, :foreign_key =>
''node_identifier''
>
> > > ....
> > > end
>
> > > but to no avail.
>
> > > It always performs the "LEFT OUTER JOIN on installations.id
> > > channel_statistics.node_identifier"
>
> > > What I want it to do is "LEFT OUTER JOIN on
> > > installations.node_identifier =
channel_statistics.node_identifier"
>
> > > Guess they might not be able to handle this but it seems unlikely
> > > somehow!
> > > Possibility that with_scope might help but I have never got that
> > > working how I want either
>
> > > Please help!!
>
> > > Thanks
>
> > > Joe
>
> > --
> > Ryan Bigghttp://www.frozenplague.net
> > Feel free to add me to MSN and/or GTalk as this email.--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
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Rails - Jan 2008 - has_many/belongs_to relationship that doesn't use id

has_many/belongs_to relationship that doesn''t use id

Re: has_many/belongs_to relationship that doesn''t use id

Re: has_many/belongs_to relationship that doesn''t use id

Re: has_many/belongs_to relationship that doesn''t use id