Wolfmans Howlings: Paginating acts_as_taggable with will_paginate

Paginating acts_as_taggable with will_paginate

Jim Morris — Thu, 12 Feb 2009 15:28:58 -0800

A question I see asked a lot is how do I paginate acts_as_taggable (on steroids)?

I haven't seen any answers I liked, so I created my own, which I'm sure a few people won't like either ;) But it works for me (tm).

I use will_paginate, but this does not work with custom finds that plugins define themselves, as is the case with acts_as_taggable.

If you do use a custom find_by_sql you have to hit the database twice, once to find the total number of items and then the paginated find.

I have a situation where I generate a tag cloud with every page, and part of that tag cloud has already calculated the number of tags for each classification I use.

I combined this with the paginator gem to get myself pages without too many hits to the database.

The first thing I do is pass the total count I get from the tag cloud to the action that renders the index for all those items matching the cloud... If you look at the article cited above I make this modification, this is dumbed down a bit for the sake of simplicity...

  tags= Post.tag_counts(:order => 'tags.name')
          tags.each do |t|
            link_to(h(t.name), tagged_post_path(:tag => t.name, :cnt => t.count))
          end

This passes the count I have already calculated to the action that will list the paginated results.

In my controller I do this to get the paginated results using will_paginate and the Pagination gem...

    def tagged
            ...
              # page if we can
              size= params[:cnt]
              if size
                per_page= 10
        
                # use Paginator gem to do the actual paging
                pager = ::Paginator.new(size, per_page) do |offset, per_page|
                  Post.find_tagged_with(params[:tag], :limit => per_page, :offset => offset)
                end
        
                # default to page 1 if not specified
                page= params[:page] || 1
        
                # gets a paged array of posts
                @posts= returning WillPaginate::Collection.new(page, per_page, size) do |p|
                  p.replace pager.page(page).items
                end
              else
                # fall back if we don't know the size
                @posts= Post.find_tagged_with(params[:tag])
              end
        
              render :action => 'index'
            end

This fits in nicely with the tag cloud I need to calculate, and it uses will_paginate just like the regular index action does.

UPDATE

I refactored this to be more generally useful, I added the following as a protected method in application.rb...

  # paginate a call to find_tagged_with
          # klass is the tagged class
          # tag is the tag to find
          # count is the total number of items with that tag, if nil count_tags is called
          # per_page is numbe rof items per page
          # page is the page we are on
          # order is the order to return the items in
          def tag_paginator(klass, tag, count=nil, per_page=10, page=1, order='updated_at DESC')
            count ||= klass.count_tags(tag)
            pager = ::Paginator.new(count, per_page) do |offset, per_page|
              klass.find_tagged_with(tag, :order => order, :limit => per_page, :offset => offset)
            end
        
            page ||= 1
        
            returning WillPaginate::Collection.new(page, per_page, count) do |p|
              p.replace pager.page(page).items
            end
          end

I call it from one of my other actions like this...

@faqs= tag_paginator(Post, 'FAQ', nil, per_page, params[:page], 'updated_at DESC')

Passing in nil as the third parameter causes the tag_paginator method to call Post.count_tags which is not part of the acts_as_taggable methods, I added it to the SingletonMethods module myself...

module ActiveRecord
          module Acts #:nodoc:
            module Taggable #:nodoc:
              module SingletonMethods
        
              ...
        
                # Return the count of tag tags in this class
               def count_tags(tag)
                 count_by_sql("select count(*) FROM tags, taggings WHERE " + sanitize_sql(['name = ? AND tags.id = taggings.tag_id AND taggable_type = ?', tag, name]))
               end
        
              ....

If you don't want to hack acts_as_taggable then simply leave that part out and call the count_by_sql yourself.

My refactored tagged action from above now looks like this...

def tagged
          ...
          tag= params[:tag]
          per_page= 10
          size= params[:cnt]
          @posts= tag_paginator(Post, tag, size, 10, params[:page])

UPDATE Johns suggestion works as of today (2/12/2009) so none of the above is needed...

  options = Car.find_options_for_tagged_with(params[:tag_name]).merge :page => params[:page] @cars = Car.paginate(options)

or my example from above...

 opts= Faq.find_options_for_tagged_with('FAQ')
         @faqs= Faq.paginator(opts.merge(:page => params[:page]))

"Paginating acts_as_taggable with will_paginate" by Eric

Wed, 15 Aug 2007 02:30:32 -0700

I found this working with `acts_as_taggable` and `will_paginate`. `@events = Event.paginate_by_id(Event.find_tagged_with(params[:id]), :page => params[:page])` Maybe there is a more graceful way.

"Paginating acts_as_taggable with will_paginate" by John Wong

Wed, 12 Sep 2007 01:51:22 -0700

Hey man.... seriously .. u dont have to put so much work just to get it to work. Just use `acts_as_taggable_on_sterioids` ... And use 2 simple lines options = Car.find_options_for_tagged_with(params[:tag_name]).merge :page => params[:page] @cars = Car.paginate(options)

"Paginating acts_as_taggable with will_paginate" by Dave

Fri, 19 Oct 2007 17:03:59 -0700

This works unless you have `:match_all` => true in there. Once you do that, a group by is added that causes `will_paginate` to get a MySQL syntax error. Still working on a way to fix it...

"Paginating acts_as_taggable with will_paginate" by Aaron H.

Mon, 26 Nov 2007 18:09:51 -0800

Dave, I found this article while having the same problem. The SQL error when using :match\_all => true has to do with the will\_paginate trying to count via the select created by acts\_as\_taggable. My solution was to add the following line to the beginning of the wp\_count! function in finder.rb of will\_paginate: `options[:select].sub!(/\.\*/, '\1.id') if options[:select] #count by id's, not wildcard (\*)` This will work unless the table you are counting does not have an id column, but using active record that should be extremely rare. If that's the case, you could always have it find the name of the class's key field.

"Paginating acts_as_taggable with will_paginate" by wolfmanjm

Tue, 27 Nov 2007 18:17:06 -0800

the match_all option doesn't work on postgresql anyway, I found a different workaround that uses a subselect to find the ids, then looks up using IN (ids,..) if anyone needs it let me know and I'll post it.

"Paginating acts_as_taggable with will_paginate" by goodwill

Sat, 05 Jan 2008 01:37:06 -0800

I tried John Wong's comment but seems not working... (Dave u are referring to this right?) I really think if such way would work its very clean.

"Paginating acts_as_taggable with will_paginate" by Henry

Sat, 05 Jan 2008 14:36:06 -0800

i had an sql error using John's comment. Aaron's solution seems to work though.

"Paginating acts_as_taggable with will_paginate" by P jam aka the nerb

Thu, 27 Mar 2008 04:34:31 -0700

Eric, a whole rails version later and using steroids, and still your 'eloquent' code snippet works great for me. since i'm trying to keep my plugins as natural as possible, i thank you. oh and you too dave.

"Paginating acts_as_taggable with will_paginate" by P jam aka the nerb

Thu, 27 Mar 2008 04:39:47 -0700

errr, dave = jim, wolfman, whathaveyou.

"Paginating acts_as_taggable with will_paginate" by COP

Wed, 23 Apr 2008 01:09:37 -0700

yes Eric's solution works for me too... one line thats it. I M LOVING RoR!!!

"Paginating acts_as_taggable with will_paginate" by rohit /pathakorama1@gmail.com

Tue, 30 Sep 2008 23:30:10 -0700

hi sir ,could you help me please i am using both the plugin will paginate and acts as taggble steroids) i have the model Article which is acts_as_taggable when i try to save the article withs tags it give me error stack level too deep vendor/plugins/will paginate/lib/will_paginate/finder.rb:163:in `method_missing_without_paginate' vendor/plugins/will paginate/lib/will_paginate/finder.rb:164:in `method_missing' vendor/plugins/acts_as_taggable/lib/acts_as_taggable.rb:172:in `save_tags'

"Paginating acts_as_taggable with will_paginate" by Flavio Granero

Wed, 12 Nov 2008 17:46:52 -0800

Hey Guys, to make the John code works, just change the method name `find_options_for_tagged_with` by `find_options_for_find_tagged_with`.

"Paginating acts_as_taggable with will_paginate" by samotage

Thu, 26 Feb 2009 16:58:12 -0800

Hey, I banged away at this for a while, then it occured to me there has to be a simpler way? So I paginated the results of the find tagged with, and bingo! @contacts = Contact.find_tagged_with(params[:tag]).paginate(:page => params[:page], :per_page => 15) Hope this helps, Sam.

"Paginating acts_as_taggable with will_paginate" by Rob

Thu, 02 Apr 2009 12:44:57 -0700

@samotage - What you propose works well but judging by the SQL in my logs, it looks like it is still pulling all the records for each page? I don't see any LIMIT in the SQL statements when using .find().paginate(). In other words, on the front end, the pagination helper is giving the correct number of pages and each page is showing the correct records. But it looks like ActiveRecord is fetching the entire unpaged recordset for each page. I'm new to Ruby and Rails so maybe I'm just missing something.

"Paginating acts_as_taggable with will_paginate" by James Rissler

Thu, 09 Apr 2009 10:16:43 -0700

I found Eric's method to work best. No need to change either plug-in. Worked for me with the latest version of rails + plugins.

"Paginating acts_as_taggable with will_paginate" by Gudata

Thu, 04 Jun 2009 09:45:21 -0700

Eric solution is working perfect for me @events = Event.paginate_by_id(Event.find_tagged_with(params[:id]), :page => params[:page]) 10x!

"Paginating acts_as_taggable with will_paginate" by 司徒正美

Sun, 28 Jun 2009 21:53:12 -0700

Thank you,John Wong!You're a genius! def tag options = Lemma.find_options_for_find_tagged_with(params[:id]).merge(:page => params[:page] ||1,:per_page =>3 ) @lemmas = Lemma.paginate(options) end

"Paginating acts_as_taggable with will_paginate" by 司徒正美

Sun, 28 Jun 2009 22:01:00 -0700

my platform:
rails2.3.2
windowxp
will_paginate 2.3.11
acts_as_taggable_on_steroids1.1

"Paginating acts_as_taggable with will_paginate" by kayen

Sun, 06 Sep 2009 21:19:43 -0700

@ wolfmanjm How did you get the match_all working in postgres? I'm also stuck at the same issue and would like to see your take on it! Thanks.

"Paginating acts_as_taggable with will_paginate" by wolfmanjm

Sun, 06 Sep 2009 21:33:06 -0700

That was almost 2 years ago :) I'll have to do some research to see how I did it.. I'll get back to you.