On Thursday, April 16, 2015 at 4:20:28 PM UTC-7, Steven Ringo wrote:
>
> Hi,
>
> I am trying to do pagination on the parent of a model association, yet
> show all the associated children for each "page" of parents.
>
> Ideally I would like to use a library like will_paginate or kaminari to
> save myself some effort creating the rendered, paged views.
>
> I have the following models in a Rails app:
>
> class Recipient < Sequel::Model
> one_to_many :devicesend
> class Device < Sequel::Model
> many_to_one :recipientsend
>
> i.e. Each Recipient has one or more Devices
>
> To paginate on Recipient but show all Devices for each page of recipients
> respectively, in SQL something like this works:
>
> SELECT
> paged_recipients.first_name, paged_recipients.last_name, devices.*FROM
> (
> SELECT first_name, last_name
> FROM recipients ORDER by id OFFSET 10 LIMIT 10
> ) paged_recipientsINNER JOIN
> devices ON paged_recipients.id = devices.recipient_idORDER BY
> paged_recipients.id
>
> Any idea if this can this be done in Sequel, ideally using the pagination
> extension?
>
> Any help would be hugely appreciated.
>
Assuming that doing it in a two queries instead of a single query is
acceptable:
Recipient.eager(:devices).paginate(2, 10).all
That will give you Recipient instances with the devices association
preloaded.
It's certainly possible to do what you want it in a single query:
Device.join(Recipient.order(:id).paginate(2, 10).as(:paged_recipients),
:id=>:recipient_id).
order(:paged_recipients__id).
select_all(:devices).
select_append(:paged_recipients__first_name,
:paged_recipients__last_name).all
That gives you Device instances that also include the first and last names
of the related recipient.
Thanks,
Jeremy
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