Question

I’m using find_by_sql to execute an SQL query.
I would like to be able to use Soundex and Levenshtein, but in order to use Levenshtein I need to include the function as a file.

This is my code so far:

info = params[:email].split('@')
name = info[0]
domain = info[1]

levenshtein = File.open("./lib/assets/mysql-function-levenshtein.sql")

results = Domain.find_by_sql(
    "" + levenshtein + "
    SELECT *
    FROM domains
    WHERE domain = '" + domain + "'"
)

I have no idea if simply including it in the query is even valid.

What’s the best implementation?

By the way the file I’m trying to include is this:
https://github.com/vyper/levenshtein-sql

Answer 1

First off, I think you’d be better off just defining that function in your database with a migration, so you wouldn’t have to define it again for every query where you want to use it:

class AddLevenShteinFunctionToDatabase < ActiveRecord::Migration
  def up
    levenshtein = File.read("/path/to/levenshtein.sql")
    execute levenshtein
  end

  def down
    # maybe put some code here to delete the function
  end
end

With this done, you could also add a scope to your Domain model for doing these kind of queries:

scope :levenshtein, lambda {|s1, s2| select("levenshein(#{s1}, #{s2})") }

With this, you should be able to write your queries something like this:

results = Domain.levenshtein("LEONARDO", "LEONARDU").where(:domain => domain)