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While creating a small CGI web application in Ruby the question came up about how much slower ActiveRecord is than DBI. Considering that ActiveRecord is initialized each time the CGI runs the performance hit could be significant.

So why not use Rails instead? The server that I am running the application on has limited resources. Rails is reported to need about 20 MB of memory and the node I have is already paging out memory to disk.

To emulate the webserver getting hit repeatedly with connections I created a connect_dbi.rb and and connect_ar.rb that insert the same row into a Tests database table. The ActiveRecord test also has the model file test.rb

The test was run using a PostGreSQL database on Ubuntu 5.10 with Ruby 1.8.4. The table was truncated between tests. I just wanted to get an idea of the performance difference between ActiveRecord and DBI. So this isn’t the strictest performance test but does provide an idea of the magnitude of difference.

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I was looking at implementing a luhn and credit card type check the other day in java and I noticed that there seems to be a lack of code for doing this in ruby. So I figured I would put something together for doing the checks in ruby.

The following function will do a luhn check for a given number (any number not just credit card numbers). The luhn algorithm is fairly simple, if you want to learn more about it check here.

def luhnCheck(ccNumber)
  ccNumber = ccNumber.gsub(/\D/, '')
  cardLength = ccNumber.length
  parity = cardLength % 2

  sum = 0
  for i in 0...cardLength
    digit = ccNumber[i] - 48

    if i % 2 == parity
      digit = digit * 2
    end

    if digit > 9
      digit = digit - 9
    end

    sum = sum + digit
  end

  return (sum % 10) == 0
end

Before running the luhn check you may want to verify that you have a valid card type or at least one you want to accept. The following function will do that based on the current bin ranges for the differenct companies as of today (for more on this see the following: credit card number information and BIN range information). N.B. Bin ranges change from time to time so this will become dated. It should be easy enough to find the updated ranges.

def ccTypeCheck(ccNumber)
  ccNumber = ccNumber.gsub(/\D/, '')
  case ccNumber
    when /^3[47]\d{13}$/ then return "AMEX"
    when /^4\d{12}(\d{3})?$/ then return "VISA"
    when /^5\d{15}|36\d{14}$/ then return "MC"
    when /^6011\d{12}|650\d{13}$/ then return "DISC"
    when /^3(0[0-5]|8[0-1])\d{11}$/ then return "DINERS"
    when /^(39\d{12})|(389\d{11})$/ then return "CB"
    when /^3\d{15}|1800\d{11}|2131\d{11}$/ then return "JCB"
    else return "NA"
  end
end

At work I received an email from someone that listed libraries I should use when connecting to their AS400 system. I wanted a quick way to convert their whitespace table into a nice comma-separated list. Below is the first 6 lines from about 50 or so.

Sequence
 number   Library
    10    QTEMP            

    20    DDMFLIB2
....

If it’s computable but a one-off, I immediately go to Ruby nowadays. 10 years ago it would have been Perl, 15 or 20 years ago the choice would have been probably a meld of sed|awk.

I always go with __END__ in these situations; Ruby stops processing at the __END__ line, but you are given an enumerable access to the contents that follow with the magical DATA object.

matches = DATA.collect { |line| line.match(/\\s+\\d+\\s+(\\w+)/) }
matches.compact!
puts matches.collect { |match| match[1] }.join(', ')

__END__
Initial library list:                            

Sequence
 number   Library
    10    QTEMP            

    20    DDMFLIB2
    30    APPSDEV
    50    FILES2                                                       

   110    QRPG                                                              

Let’s try it out (running Ruby/Windows in a Cygwin terminal):

dday@xpmachine21 ~
$ ruby liblist.rb
QTEMP, DDMFLIB2, APPSDEV, FILES2, QRPG

Success!