From a7915495880ae091b626e8b313c5c75f1f6fbf36 Mon Sep 17 00:00:00 2001
From: Norman Clarke <norman@randomba.org>
Date: Thu, 23 Oct 2008 21:40:22 -0200
Subject: [PATCH] Added support for :order => :random in queries.

---
 activerecord/lib/active_record/base.rb             |    6 +++---
 .../connection_adapters/abstract_adapter.rb        |   14 ++++++++++++++
 .../connection_adapters/mysql_adapter.rb           |   10 +++++++++-
 activerecord/test/cases/finder_test.rb             |    5 +++++
 activerecord/test/cases/named_scope_test.rb        |    5 +++++
 5 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index b89c864..f5b3017 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1669,10 +1669,10 @@ module ActiveRecord #:nodoc:
           scope = scope(:find) if :auto == scope
           scoped_order = scope[:order] if scope
           if order
-            sql << " ORDER BY #{order}"
-            sql << ", #{scoped_order}" if scoped_order
+            sql << " ORDER BY #{connection.order(order)}"
+            sql << ", #{connection.order(scoped_order)}" if scoped_order
           else
-            sql << " ORDER BY #{scoped_order}" if scoped_order
+            sql << " ORDER BY #{connection.order(scoped_order)}" if scoped_order
           end
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index c518335..8d6a247 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -93,6 +93,20 @@ module ActiveRecord
         yield
       end
 
+      # DATABASE STATEMENTS ======================================
+
+      # Adjust ORDER BY arguments to match supported syntax. Passing :random
+      # will return the appropriate RAND()/RANDOM()/etc for the adapter. All
+      # other arguments are returned unmodified.
+      def order(arg)
+        case arg
+        when :random
+          "RANDOM()"
+        else
+          arg
+        end
+      end
+
       # CONNECTION MANAGEMENT ====================================
 
       # Checks whether the connection to the database is still active. This includes
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index 1e452ae..a43b306 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -354,7 +354,15 @@ module ActiveRecord
           end
         end
       end
-
+    
+      def order(arg)
+        case arg
+        when :random
+          "RAND()"
+        else
+          arg
+        end
+      end
 
       # SCHEMA STATEMENTS ========================================
 
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index 153880a..5722bc9 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -175,6 +175,11 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal 4, developers.map(&:salary).uniq.size
   end
 
+  def test_find_with_random_order
+    developers =  Developer.find(:all, :order => :random, :limit => 4)
+    assert_equal 4, developers.size
+  end
+
   def test_find_with_entire_select_statement
     topics = Topic.find_by_sql "SELECT * FROM topics WHERE author_name = 'Mary'"
 
diff --git a/activerecord/test/cases/named_scope_test.rb b/activerecord/test/cases/named_scope_test.rb
index 64e8997..67c434d 100644
--- a/activerecord/test/cases/named_scope_test.rb
+++ b/activerecord/test/cases/named_scope_test.rb
@@ -158,6 +158,11 @@ class NamedScopeTest < ActiveRecord::TestCase
     expected_proxy_options = { :conditions => { :approved => true } }
     assert_equal expected_proxy_options, Topic.approved.proxy_options
   end
+  
+  def test_random_order
+    topics = Topic.base.all(:order => :random, :limit => 4)
+    assert_equal 4, topics.size
+  end
 
   def test_first_and_last_should_support_find_options
     assert_equal Topic.base.first(:order => 'title'), Topic.base.find(:first, :order => 'title')
-- 
1.6.0