Rails - Oct 2011 - Different Order by clause on will_paginate pages?

Hi im trying to list random records on first page and from 2nd page to
onwards, i need to show records by created_at using will_paginate plugin
but i can only apply one of these condition at a time.

Im showing based on order clause e,g

Order(''RAND()'') or Order(''created_at Desc'')

And then applying pagination on it. I don''t know how to apply both of
them with Random on ist page and created at on the rest of the
pagination. Anybody have any idea?

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On Oct 26, 10:25 am, Hussam Ali
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Hi im trying to list random records on first page and from 2nd page to
> onwards, i need to show records by created_at using will_paginate plugin
> but i can only apply one of these condition at a time.
>
> Im showing based on order clause e,g
>
> Order(''RAND()'') or Order(''created_at
Desc'')
>
> And then applying pagination on it. I don''t know how to apply both
of
> them with Random on ist page and created at on the rest of the
> pagination. Anybody have any idea?
>
That sounds like two mutually contradictory aims. You could perhaps
have a single ''random'' page and then a series of paginated by
created_at pages.
If you absolutely had to present the illusion of the first page being
a random selection, you could also fiddle with the page parameter - if
it''s 1 show a random selection, if it''s greater than one
subtract 1
and pass that to will_paginate

Fred
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Frederick Cheung wrote in post #1028581:
> On Oct 26, 10:25am, Hussam Ali
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>> pagination. Anybody have any idea?
>>
>
> That sounds like two mutually contradictory aims. You could perhaps
> have a single ''random'' page and then a series of
paginated by
> created_at pages.
> If you absolutely had to present the illusion of the first page being
> a random selection, you could also fiddle with the page parameter - if
> it''s 1 show a random selection, if it''s greater than one
subtract 1
> and pass that to will_paginate
>
> Fred

Ok i got your point, i have done this and it works,

if params[:page].to_i > 1
 order by created_at
else
 order by random
end

Is there any other possible approach of handling it or how can i make
the above code more efficient??????

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On Oct 27, 2011, at 2:46 AM, Hussam Ali wrote:
> Frederick Cheung wrote in post #1028581:
>> On Oct 26, 10:25am, Hussam Ali
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>>> pagination. Anybody have any idea?
>>> 
>> 
>> That sounds like two mutually contradictory aims. You could perhaps
>> have a single ''random'' page and then a series of
paginated by
>> created_at pages.
>> If you absolutely had to present the illusion of the first page being
>> a random selection, you could also fiddle with the page parameter - if
>> it''s 1 show a random selection, if it''s greater than
one subtract 1
>> and pass that to will_paginate
>> 
>> Fred
> 
> 
> Ok i got your point, i have done this and it works,
> 
> if params[:page].to_i > 1
> order by created_at
> else
> order by random
> end
> 
> Is there any other possible approach of handling it or how can i make
> the above code more efficient??????
> 
I think you''re missing one thing here. This precise construction means
that there is a significant chance that some items will never be seen at all. If
the first "page" is random, it''s not "random within the
parameters of what would otherwise land on page 1", it''s
"random across the entire database". And then you move to page 2,
where it''s created_at über alles.

What I would do is have a separate route for "random tease of
what''s in the database", and then have a real "everything, in
order" route as is normal for an index + pagination.

Walter
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> I think you''re missing one thing here. This precise construction
means
> that there is a significant chance that some items will never be seen at
> all. If the first "page" is random, it''s not
"random within the
> parameters of what would otherwise land on page 1", it''s
"random across
> the entire database". And then you move to page 2, where it''s
created_at
> ber alles.
>
> What I would do is have a separate route for "random tease of
what''s in
> the database", and then have a real "everything, in order"
route as is
> normal for an index + pagination.
Thanks Walter, it would certainly miss some of the items, but what you
are saying to have separate route for random and for pagination is may
be possible but right now i do not understand how to implement this, but
i will try to do it and if u can elaborate it further with example then
it would be helpful for me.

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On Oct 27, 2011, at 10:02 AM, Hussam Ali wrote:
>> I think you''re missing one thing here. This precise
construction means
>> that there is a significant chance that some items will never be seen
at
>> all. If the first "page" is random, it''s not
"random within the
>> parameters of what would otherwise land on page 1", it''s
"random across
>> the entire database". And then you move to page 2, where
it''s created_at
>> ber alles.
>> 
>> What I would do is have a separate route for "random tease of
what''s in
>> the database", and then have a real "everything, in
order" route as is
>> normal for an index + pagination.
> 
> Thanks Walter, it would certainly miss some of the items, but what you
> are saying to have separate route for random and for pagination is may
> be possible but right now i do not understand how to implement this, but
> i will try to do it and if u can elaborate it further with example then
> it would be helpful for me.
#foos_controller.rb

def sample
  @foos = Foo.order(''RAND()'').limit(20) #mysql
  #@foos = Foo.order(''RANDOM()'').limit(20) #sqlite
end

routes.rb

resources :foos do
  collection do
    get ''sample''
  end
end

#foos/sample.html.erb
<h1>Hey look at all the cool foos we have!</h1>
<%= render @foos %>

#foos/_foo.html.erb
<div class="foo">
<p><%= foo.name %></p>
<p><%= foo.rank %></p>
<p><%= foo.serial_number %></p>
</div>

And then your index.html.erb would be exactly the same as it currently is, with
the pagination and whatnot, and your index (controller) method would also be the
same, with no worries about making the pagination smarter. Wherever you wanted
your random sample to appear, you would simply use the sample method. And your
index would be a normal index without any notion of randomness, so any possible
foo could be shown or found.

Walter
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> And then your index.html.erb would be exactly the same as it currently
> is, with the pagination and whatnot, and your index (controller) method
> would also be the same, with no worries about making the pagination
> smarter. Wherever you wanted your random sample to appear, you would
> simply use the sample method. And your index would be a normal index
> without any notion of randomness, so any possible foo could be shown or
> found.
Thanks Walter, i appreciate your efforts, i understand your point here,
but what you are saying is to have two separate things, my point is to
show random items with pagination, we can show random items as shown
above but we cannot accommodate this thing with our overall pagination,
e.g

def index
  @foo = Foo.order(''created_at Desc'').paginate :page =>
params[:page],
:per_page => @per_page
end

As u are saying this would remain the same but my point is that we have
to accommodate that random sample method in the first page rather than
to have it separate from pagination. As in the above index method how
can we pass sample in it just for first page?

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On Oct 28, 2011, at 3:15 AM, Hussam Ali wrote:
>> And then your index.html.erb would be exactly the same as it currently
>> is, with the pagination and whatnot, and your index (controller) method
>> would also be the same, with no worries about making the pagination
>> smarter. Wherever you wanted your random sample to appear, you would
>> simply use the sample method. And your index would be a normal index
>> without any notion of randomness, so any possible foo could be shown or
>> found.
> 
> Thanks Walter, i appreciate your efforts, i understand your point here,
> but what you are saying is to have two separate things, my point is to
> show random items with pagination, we can show random items as shown
> above but we cannot accommodate this thing with our overall pagination,
> e.g
> 
> def index
>  @foo = Foo.order(''created_at Desc'').paginate :page =>
params[:page],
> :per_page => @per_page
> end
> 
> As u are saying this would remain the same but my point is that we have
> to accommodate that random sample method in the first page rather than
> to have it separate from pagination. As in the above index method how
> can we pass sample in it just for first page?
I''m making a more fundamental point. If you randomize the sort when
making your first page, it may not contain some elements that would ordinarily
be found in the first page (when sorted deterministically). So you look at those
things, and then you move on to page 2, which may contain elements you already
saw on page 1 (remember, that was randomized) along with the rest of the next
page of sorted elements. And so on. So at each page after 1, you have a fair
chance of seeing a repeat, and you also have a statistically high chance of
never seeing some of the elements that would have appeared on the first page,
and this chance goes up the larger your total population of elements becomes.
When you move to page 2, your sorting mechanism assumes you''ve seen
everything that would sort to page 1, and never shows it to you again.

Walter

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