mongod_db_query.rb

require 'rubygems'
require 'test/unit'
require 'mongo'


def rating(query)
  collection_size = query.collection.count
  return 100 if collection_size <= 1
  explanation = query.explain
  return   0 if collection_size >  1 and explanation['startKey'].empty? 
  convert(explanation['nscanned']/collection_size) + 50*(explanation['n']/explanation['nscanned'])
end
def convert(ratio)
  ((ratio * -100) + 100) / 2
end


class QueryTest < Test::Unit::TestCase
  include Mongo
  
  def setup
    @col = create_collection
  end
  
  def test_indexed_read_on_a
    query_to_test = @col.find({'a' => 3})
    assert_operator  50, :<=, rating(query_to_test), "Low query rating (<50)"
    assert_operator 100, :<=, rating(query_to_test), "Less than outstanding query rating (<100)"
  end 
  
  def create_collection(name = 'sample', db_name = 'aDB')
    db = Connection.new.db(db_name)
    db.drop_collection(name) if db.collection_names.include? name 
    col = db[name]
    100.times { |i| col.insert({:a => i, :b => 10 + i}) }	
    col.create_index('a')
    col  
  end
end