refactoring + specs

README.markdown

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+PROBLEM
+=======
+ - database :order=>'random' is slow
+ - active record has no random build in
+
+SOLUTION
+========
+ - count all records
+ - grab x records from rand(offset)
+
+INSTALL
+=======
+`script/plugin install git://github.com/grosser/random_records.git`
+
+USAGE
+=====
+
+    Model.random(3) == [Model(id:112),Model(id:113),Model(id:114)]
+    Model.random(1) == [Model(id:322)]
+    Model.random == Model(id:234)
+
+AUTHOR
+======
+Michael Grosser  
+grosser.michael@gmail.com  
+Hereby placed under public domain, do what you want, just do not hold me accountable...  

Rakefile.rb

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+require 'rubygems'
+require 'spec'
+
+desc 'Default: run spec.'
+task :default => :spec
+
+desc "Run all specs in spec directory"
+task :spec do |t|
+  options = "--colour --format progress --loadby --reverse"
+  files = FileList['spec/**/*_spec.rb']
+  system("spec #{options} #{files}")
+end

lib/random_records.rb

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+class ActiveRecord::Base
+  def self.random(num=nil,options={})
+    return_array = !num.nil?
+    num ||= 1
+    return [] if num.zero?
+    num_records = options.delete(:count) || count
+    highest_possible_offset = [0,num_records-num].max 
+    offset = [rand(num_records),highest_possible_offset].min
+    limit = [num,num_records].min
+    all = find(:all, {:offset => offset, :limit=>limit}.merge(options))
+    return_array ? all : all[0]
+  end
+end

spec/random_records_spec.rb

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+require File.expand_path("spec_helper", File.dirname(__FILE__))
+
+describe :random do
+  before :all do
+    10.times {|i| User.create!}
+  end
+
+  it "finds a record when called without parameters" do
+    User.random.class.should == User
+  end
+  it "finds a single random record" do
+    User.random(1).size.should == 1
+    User.random(1)[0].class.should == User
+  end
+  it "finds by offset from rand" do
+    User.expects(:rand).with(User.count).returns 3
+    User.random(1).should == [User.find(4)]
+  end
+  it "finds using the given count option" do
+    User.expects(:rand).with(3).returns 2
+    User.random(1,:count=>3).should == [User.find(3)]
+  end
+  it "finds the requested number" do
+    User.random(9).uniq.size.should == 9
+  end
+  it "finds sequentially from offset" do
+    users = User.random(9).map(&:id)
+    users.each_with_index do |id,index|
+      next if index.zero?
+      id.should == (users[index-1] + 1)
+    end
+  end
+  it "finds count records when requested >= count" do
+    User.random(20).size.should == User.count
+  end
+  it "returns empty array if number is 0" do
+    User.random(0).should == []
+  end
+  it "is chainable" do
+    User.first_5.random(9).size.should == 5
+    User.first_5.random(4).size.should == 4
+  end
+end
+
+describe 'when no records exist' do
+  before :all do
+    User.delete_all
+  end
+  it 'finds nil without parameters' do
+    User.random.should == nil
+  end
+  it "finds 0 for all calls" do
+    User.random(20).size.should == 0
+  end
+end

spec/setup_test_model.rb

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+require 'rubygems'
+require 'active_record'
+
+#create model table
+ActiveRecord::Schema.define(:version => 1) do
+  create_table "users" do |t|
+    t.integer :age
+    t.timestamps
+  end
+end
+
+#create model
+class User < ActiveRecord::Base
+  named_scope :first_5, :conditions=>"id < 6"
+end

spec/spec_helper.rb

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+# ---- requirements
+require 'rubygems'
+require 'spec'
+require 'mocha'
+
+$LOAD_PATH << File.expand_path("../lib", File.dirname(__FILE__))
+
+
+# ---- rspec
+Spec::Runner.configure do |config|
+  config.mock_with :mocha
+end
+
+
+# ---- bugfix
+#`exit?': undefined method `run?' for Test::Unit:Module (NoMethodError)
+#can be solved with require test/unit but this will result in extra test-output
+module Test
+  module Unit
+    def self.run?
+      true
+    end
+  end
+end
+
+# ---- load active record
+require 'active_record'
+
+
+RAILS_ENV = "test"
+ActiveRecord::Base.configurations = {"test" => {
+  :adapter => "sqlite3",
+  :database => ":memory:",
+}.with_indifferent_access}
+
+ActiveRecord::Base.logger = Logger.new(File.directory?("log") ? "log/#{RAILS_ENV}.log" : "/dev/null")
+ActiveRecord::Base.establish_connection(:test)
+
+
+# ---- setup environment/plugin
+require File.expand_path("../init", File.dirname(__FILE__))
+load File.expand_path("setup_test_model.rb", File.dirname(__FILE__))