Fixed : incompatibility with postgresql in the find_recent method

app/models/comment_activity.rb

@@ -16,10 +16,11 @@ def most_recent_comment
   class << self
     def find_recent
       Post.find(:all,
-        :select => 'distinct posts.*',
-        :joins  => 'INNER JOIN comments ON comments.post_id = posts.id',
-        :order  => 'comments.created_at DESC',
-        :limit  => 5
+        :group  => "comments.post_id, posts." + Post.column_names.join(", posts."),
+        :select => 'posts.*, max(comments.created_at), comments.post_id',
+        :joins  => 'INNER JOIN comments ON comments.post_id = posts.id', 
+        :order  => 'max(comments.created_at) desc', 
+        :limit  => 5        
       ).collect {|post|
         CommentActivity.new(post)
       }.sort_by {|activity|

spec/models/comment_activity_spec.rb

@@ -1,6 +1,43 @@
 require File.dirname(__FILE__) + '/../spec_helper'
 
 describe CommentActivity, '#comments' do
+
+  def valid_comment_attributes(extra = {})
+    {
+      :author => 'Don Alias',
+      :author_url => "me",
+      :author_email => "me@fake.com",
+      :body   => 'This is a comment',
+      :post   => Post.create!(:title => 'My Post', :body => "body", :tag_list => "ruby")
+    }.merge(extra)
+  end
+
+  context "find recent comments" do
+    before :each do      
+      @comments = []
+      (1..10).each do |n|
+        @comments << Comment.create(valid_comment_attributes(:created_at => Time.now - n * (60 * 60 * 24)))
+      end
+    end
+
+    it "should have the comment activity sorted by when they were created" do
+      comment_activity = CommentActivity.find_recent 
+      comment_activity.first.post.should == @comments.first.post
+    end
+
+    it do
+      comment_activity = CommentActivity.find_recent
+      comment_activity.should have_exactly(5).posts
+    end
+
+    it "should not return repeated posts" do
+      comment = Comment.create! valid_comment_attributes(:post => Post.first, :created_at => Time.now)
+      comment_activity = CommentActivity.find_recent
+      comment_activity.select{|a| a.post == comment.post}.size.should == 1
+    end
+
+  end
+
   it 'finds the 5 most recent approved comments for the post' do
     ret = [mock_model(Comment)]
     comments = []