Alex Le’s Blog

If you have to deal with multiple configuration values for different environments, this easy and very simple trick will let you put all these values to an external YML file and have a convenient global hash to access the values. Another benefit of putting config values in a YML file is that you can re-factor shared values into a default block, and override values in environment-specific blocks. You can keep your code DRY, now keep your config DRY as well, instead of littering your different environment config files.

In your environment.rb, add this one line between the Rails::Initializer.run do … end block

Rails::Initializer.run do |config|
  # ... other config code

  SITE_CONFIG = YAML.load_file(  "#{RAILS_ROOT}/config/site_config.yml" )[ ENV['RAILS_ENV'] || RAILS_ENV ]
end

Create a new “site_config.yml” file the /config folder using the following skeleton:

# config/site_config.yml

# the shared configurations.  Override values here in each individual environment.
defaults: &defaults
  twitter_username: your_username
  twitter_password: your_password

  # Blog
  blog_url: http://alexle.net
  blog_feed: http://alexle.net/feed/
  blog_email: 

development:
  <<: *defaults
  # override
  twitter_username: dev_username
  twitter_password: dev_password

slicehost:
  <<: *defaults

test:
  <<: *defaults

staging:
  <<: *defaults

production:
  <<: *defaults

Restart your web server so that the environment.rb file is picked up. Now within your code, you can access the values using

  logger.debug SITE_CONFIG["twitter_username"]

The only gotcha of this method is that we cannot override nested configuration blocks due to the way YML files are interpreted.

# this sample won't work
defaults: &defaults
  twitter:
    username:
    password:

development:
  <<: *defaults

  # this override doesn't work since it replaces the twitter hash in the defaults block with a new
  # hash containing only the "username" key (The "password" key-value is gone!)
  twitter:
    username: dev_username

cheers!

My good friend Stephen Celis convinced me to give Rails.vim a shot for Rails development. My vi skill is not that great yet (e.g. beginner level), so Stephen recommended vimtutor, which does not come pre-installed on my CentOS server. So here’s a quick recap of getting vimtutor installed:

1. Installing “which”, which the vimtutor script uses to detect the vi version and copy the vimtutor script accordingly.

sudo yum install which

2. Installing “vim-enhanced” package, which contains the vimtutor

sudo yum install vim-enhanced

Now you should be able to do “vimtutor” and start a new vimtutor session. Happy h-j-k-l around and stops using the arrow keys

It’s been a long time since my previous post. There was a lot that has happened (and not happened). I switched my job from being a consultant at BridgePoint Technologies, a small consulting firm in Oak Brook, to being a lead developer at Designkitchen.com. I love the team at BridgePoint, I learned and grew a lot during my time there, and of course I always remembered to have a good time wherever I go to. I had a blast, and I still keep regular contacts with friends and colleagues there. The new position at Designkitchen is also awesome in the sense that it offers new opportunities, new challenges, and a new environment. And I find life is funny in its own way. BridgePoint’s office is right across the street from the McDonald’s HQ. I used to walked across the street to lunch with friends to the yellow McDonalds restaurant near by, which impressively has a timer to tell how fast each customer is served. The average was about less than 40 seconds. Joining us were also McDonalds corporate employees grabbing a quick bite. Was it one more reason to get back to work faster to climb the corporate ladder? Anyhow, I’m currently the lead developer for ClubBK.com, a Burger King’s effort to get their presence on the so-cool cyberspace for kids. Never did I feel more like having burgers for lunch everyday. Nonetheless, I’m having a blast working side by side with the different teams at Designkitchen. Everyday is a learning experience.

I picked up a Canon Digital Rebel XSI with a 50mm f/1.4 prime lense. I knew nothing about photography, and now is always a good time to start picking up a new hobby. My grandfather is really good photographer, and I don’t want to see him disappointing that his grand kid is being ignorant of the art. I’m not. I just never had the budget ready for such a plunge. But I’m glad I did it. The XSI is an excellent camera — light, compact, good build, and cheap. Coupled with the fast f/1.4 lense, I’ve had some good (or lucky) shots of people at really low light conditions. Everybody was impressed with the photos, without knowing about my newbie status.

I also got a new Mac Book Air with 64GB SSD for rails and iPhone apps development. Designkitchen is a heavy Mac environment. Almost 100% of the creative team is on Mac (clubBK.com is 100% mac, that’s for sure), and most Rails guys I know are also on Mac. Not that I’m being influenced by peer-pressure, but definitely that counts for something. I’ve been using the Air for a straight 2 days, leaving my Dell D830 in the backpack. Heck, I don’t need a backpack for the Air! Performance wise, the machine is zippy and Rails 2.3.0 boots in merely seconds. I managed to consume more than half the 64GB with the iPhone SDK and OS X updates, but I still have plenty of room left. I have all my media on the main desktop, and for music, Last.FM and Pandora provide some awesome head-banging time when I’m not home (try some Disarmonia Mundi and you’ll know what I mean). In other words, I’m getting macimized while staying anti-vista.

I’m saving the best for last, but I’m finally free. 2.10, the day to remember. I’m so ready to have my life back. Time to make some changes and live life a bit, as I’ve been in the shadow for way too long.

I don’t like to get political on my blog, but a friend of mine sent me a link to a political quiz at ABCNews.

http://abcnews.go.com/Politics/MatchoMatic/fullpage?id=5542139

Here are my answers:

I don’t disagree with some of the things that Obama is saying, but I strongly agree with McCain’s principles and leadership. And as a foreign immigrant to this country, I’m strongly offended by Obama’s way of dealing with the issue:

Obama: “We should require them to pay a fine, learn English, and go to the back of the line for citizenship behind those who came here legally. But we cannot — and should not — deport 12 million people.” (number #8)

Who the hell is Obama to say “let’s fine these illegal immigrants because they just sneaked in the country?” JERK, JERK, and JERK. How about babies that were brought to the States by their parents, granted “illegally” according to US’s immigration laws. Do these babies do anything wrong to get fined? They speak English, pay taxes, go to school, and contribute to society as much as anyone else — while getting treated as a 2nd-class citizen.

McCain has a much clearer policy and it is towards an legalizing the integration of the immigrants (currently there’s no such thing!)

“The program will … ensure that all undocumented aliens either leave of follow the path to legal residence. American cannot permit a permanent category of individuals that do not have recognized status — a permanent second class”

McCain, I wish you the best of luck!

For a Rails/SQLServer application I’m working on, I had to deal with pagination with custom queries because of the different joins. The mislav-will_paginate plugin works great for MySQL, but for SQL Server, the paginated query generated by the current SQL Server Adapter (I’m using activerecord-sqlserver-adapter-1.0.0.9250) does not work very well. The current implementation is targetted really for SQL Server 2000 and older versions since these versions do not have support for ROW_NUMBER() method. It is a major pain in the butt to do pagination with these databases. With the newer SQL Sever 2005, the job is a bit easier. Microsoft implemented the ROW_NUMBER() method with a convoluted syntax to have better support for pagination, but it is still a drag because of the weird syntax.

Semergence wrote in his blog about patching the SQLServerAdapter to support pagination. Based on his post, I improved ActiveRecord::ConnectionAdapters::SQLServerAdapter::add_limit_offset! to make the query work in a more general way with free-form queries, e.g. queries ran with the paginate_by_sql() method provided by mislav-will_paginate

Include this script in your environment.rb file, or an external file and “require” the file within environment.rb.

  # monkey-patching SQLServerAdapter to support SQL Server 2005-style pagination
  module ActiveRecord
    module ConnectionAdapters
      class SQLServerAdapter
        def add_limit_offset!(sql, options)
          puts sql
          options[:offset] ||= 0
          options_limit = options[:limit] ? "TOP #{options[:limit]}" : ""
          options[:order] ||= if order_by = sql.match(/ORDER BY(.*$)/i)
                                order_by[1]
                              else
                                sql.match('FROM (.+?)\b')[1] + '.id'
                              end
          sql.sub!(/ORDER BY.*$/i, '')
          sql.sub!(/SELECT/i, "SELECT #{options_limit} * FROM ( SELECT ROW_NUMBER() OVER( ORDER BY #{options[:order] } ) AS row_num, ")
          sql << ") AS t WHERE row_num > #{options[:offset]}”
          puts sql
          sql
        end
      end
    end
  end

The method above monkey-patches the SQLServerAdapter by overwriting the add_limit_offset! method.

Here’s a custom query that I used and the transformed result:

Resource.paginate_by_sql([
      %!SELECT  resources.*
        	,skills_count.skill_count
        FROM resources
        	,(
        		SELECT resource_id
        			, COUNT(*) AS skill_count
        		FROM resource_skills
            WHERE meta_skill_id IN (1,2,3,4,5,6,7,8,9,10)
        		GROUP BY resource_id
        	) AS skills_count
        WHERE resources.is_active = ?
          AND resources.id = skills_count.resource_id
        ORDER BY skill_count DESC
      !, true ], :page => page, :per_page => per_page

With :page = 1, :per_page = 2, the resulted SQL is:

SELECT TOP 2 * FROM ( SELECT ROW_NUMBER() OVER( ORDER BY skill_count DESC ) AS row_num, resources.*
 	,skills_count.skill_count
 FROM resources
 	,(
 		SELECT resource_id
 			, COUNT(*) AS skill_count
 		FROM resource_skills
 WHERE meta_skill_id IN (1,2,3,4,5,6,7,8,9,10)
 		GROUP BY resource_id
 	) AS skills_count
 WHERE resources.is_active = 1
 AND resources.id = skills_count.resource_id

 ) AS t WHERE row_num > 0

The will_pagination’s COUNT query is

SELECT COUNT(*) FROM (
 SELECT resources.*
 	,skills_count.skill_count
 FROM resources
 	,(
 		SELECT resource_id
 			, COUNT(*) AS skill_count
 		FROM resource_skills
 WHERE meta_skill_id IN (21,22)
 		GROUP BY resource_id
 	) AS skills_count
 WHERE resources.is_active = 1
 AND resources.id = skills_count.resource_id
 ) AS count_table

The ORDER BY part is automatically removed from the main query (which becomes a sub-select) by the plugin to speed up the query. This in turns sanatizes the sql so that SQL Server doesn’t not complain about nested “ORDER BY” within a sub-select. Neat!

The only catch with the current add_limit_offset! is that it does not support ALIAS-ing, because the aliasing confuses the reqex to parse out the ORDER BY condition in the OVER() part of the query.

For regular find() queries, here’s a sample result

Resource.find(:first)
# original query:  SELECT * FROM resources
# transformed:   SELECT TOP 1 * FROM ( SELECT ROW_NUMBER() OVER( ORDER BY resources.id ) AS row_number, * FROM resources ) AS t WHERE row_num > 0

Hope this helps and cheers!