How to specify Ruby regex when using Active Record in Rails?

Question

To get all jobs which invoice_number is a pure number I do:

Job.where("invoice_number REGEXP '^[[:digit:]]+$'")

Is it possible to do the same by specifying the regex in Ruby rather than MySQL ?

Answer 1

One way is

Job.all.select{|j| j =~ /^\d+$/}

but it will not be as efficient as the MySQL version.

Another possibility is to use a named scope to hide the ugly SQL:

  named_scope :all_digits, lambda { |regex_str|
    { :condition => [" invoice_number REGEXP '?' " , regex_str] }
  }

Then you have Job.all_digits.

Note that in the second example, you are assembling a query for the database, so regex_str needs to be a MySQL regex string instead of a Ruby Regex object, which has a slightly different syntax.