Do not allow requests for search results after the first 500

The pages for these search results are extremely slow to load. This
is not an ideal solution by any means. Really we want to dig into why
high offsets are so slow, and whether there's anything we can do to
fix that.

3 files changed, 21 insertions, 3 deletions

diff --git a/app/controllers/general_controller.rb b/app/controllers/general_controller.rb
index 2c8abbaf4..6aef0cb1b 100644
--- a/app/controllers/general_controller.rb
+++ b/app/controllers/general_controller.rb
@@ -9,6 +9,8 @@ require 'open-uri'
 
 class GeneralController < ApplicationController
 
+    MAX_RESULTS = 500
+
     # New, improved front page!
     def frontpage
         medium_cache
@@ -124,11 +126,18 @@ class GeneralController < ApplicationController
             end
         end
 
+        @page = get_search_page_from_params
+
         # Query each type separately for separate display (TODO: we are calling
         # perform_search multiple times and it clobbers per_page for each one,
         # so set as separate var)
         requests_per_page = params[:requests_per_page] ? params[:requests_per_page].to_i : 25
 
+        # Later pages are very expensive to load
+        if @page > MAX_RESULTS / requests_per_page
+            raise ActiveRecord::RecordNotFound.new("Sorry. No pages after #{MAX_RESULTS / requests_per_page}.")
+        end
+
         @this_page_hits = @total_hits = @xapian_requests_hits = @xapian_bodies_hits = @xapian_users_hits = 0
         if @requests
             @xapian_requests = perform_search([InfoRequestEvent], @query, @sortby, 'request_collapse', requests_per_page)
@@ -138,6 +147,7 @@ class GeneralController < ApplicationController
             @xapian_requests_total_hits = @xapian_requests.matches_estimated
             @total_hits += @xapian_requests.matches_estimated
             @request_for_spelling = @xapian_requests
+            @max_requests = (@xapian_requests.matches_estimated > MAX_RESULTS) ? MAX_RESULTS : @xapian_requests.matches_estimated
         end
         if @bodies
             @xapian_bodies = perform_search([PublicBody], @query, @sortby, nil, 5)
@@ -147,6 +157,7 @@ class GeneralController < ApplicationController
             @xapian_bodies_total_hits = @xapian_bodies.matches_estimated
             @total_hits += @xapian_bodies.matches_estimated
             @request_for_spelling = @xapian_bodies
+            @max_bodies = (@xapian_bodies.matches_estimated > MAX_RESULTS) ? MAX_RESULTS : @xapian_bodies.matches_estimated
         end
         if @users
             @xapian_users = perform_search([User], @query, @sortby, nil, 5)
@@ -156,6 +167,7 @@ class GeneralController < ApplicationController
             @xapian_users_total_hits = @xapian_users.matches_estimated
             @total_hits += @xapian_users.matches_estimated
             @request_for_spelling = @xapian_users
+            @max_users = (@xapian_users.matches_estimated > MAX_RESULTS) ? MAX_RESULTS : @xapian_users.matches_estimated
         end
 
         # Spelling and highight words are same for all three queries
diff --git a/app/views/general/search.html.erb b/app/views/general/search.html.erb
index 3914a2f30..0a04f544e 100644
--- a/app/views/general/search.html.erb
+++ b/app/views/general/search.html.erb
@@ -160,7 +160,7 @@
           <% end %>
         </div>
 
-        <%= will_paginate WillPaginate::Collection.new(@page, @bodies_per_page, @xapian_bodies.matches_estimated) %>
+        <%= will_paginate WillPaginate::Collection.new(@page, @bodies_per_page, @max_bodies) %>
       </div>
        <% elsif @variety_postfix == 'bodies' %>
           <p><%= raw(_('<a href="{{browse_url}}">Browse all</a> or <a href="{{add_url}}">ask us to add one</a>.', :browse_url => list_public_bodies_default_path.html_safe, :add_url => (help_requesting_path + '#missing_body').html_safe)) %></p>
@@ -179,7 +179,7 @@
             <%= render :partial => 'user/user_listing_single', :locals => { :display_user => result[:model] } %>
           <% end %>
         </div>
-        <%= will_paginate WillPaginate::Collection.new(@page, @users_per_page, @xapian_users.matches_estimated) %>
+        <%= will_paginate WillPaginate::Collection.new(@page, @users_per_page, @max_users) %>
 
       </div>
     <% end %>
@@ -199,7 +199,7 @@
           <% end %>
         </div>
 
-        <%= will_paginate WillPaginate::Collection.new(@page, @requests_per_page, @xapian_requests.matches_estimated) %>
+        <%= will_paginate WillPaginate::Collection.new(@page, @requests_per_page, @max_requests) %>
       </div>
     <% end %>
 <% end %>
diff --git a/spec/controllers/general_controller_spec.rb b/spec/controllers/general_controller_spec.rb
index cb00b301c..8652d9b17 100644
--- a/spec/controllers/general_controller_spec.rb
+++ b/spec/controllers/general_controller_spec.rb
@@ -262,4 +262,10 @@ describe GeneralController, 'when using xapian search' do
         response.body.should include('Track this search')
     end
 
+    it 'should not show high page offsets as these are extremely slow to generate' do
+        lambda {
+            get :search, :combined => 'bob/all', :page => 25
+        }.should raise_error(ActiveRecord::RecordNotFound)
+    end
+
 end