From 1ba8ac0848f40c7fa18c9e7bdac944a50d3c348c Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Fri, 10 Sep 2010 13:36:42 -0700
Subject: differentiating equality and assignment

---
 lib/arel/nodes.rb            |  1 +
 lib/arel/nodes/assignment.rb |  6 ++++++
 lib/arel/update_manager.rb   |  2 +-
 lib/arel/visitors/to_sql.rb  | 15 +++++++++++++--
 4 files changed, 21 insertions(+), 3 deletions(-)
 create mode 100644 lib/arel/nodes/assignment.rb

diff --git a/lib/arel/nodes.rb b/lib/arel/nodes.rb
index 1215f3f00c..1f31219417 100644
--- a/lib/arel/nodes.rb
+++ b/lib/arel/nodes.rb
@@ -1,5 +1,6 @@
 require 'arel/nodes/binary'
 require 'arel/nodes/equality'
+require 'arel/nodes/assignment'
 require 'arel/nodes/or'
 require 'arel/nodes/and'
 require 'arel/nodes/greater_than'
diff --git a/lib/arel/nodes/assignment.rb b/lib/arel/nodes/assignment.rb
new file mode 100644
index 0000000000..693bd5afe6
--- /dev/null
+++ b/lib/arel/nodes/assignment.rb
@@ -0,0 +1,6 @@
+module Arel
+  module Nodes
+    class Assignment < Arel::Nodes::Binary
+    end
+  end
+end
diff --git a/lib/arel/update_manager.rb b/lib/arel/update_manager.rb
index cd4342529b..484230c4e1 100644
--- a/lib/arel/update_manager.rb
+++ b/lib/arel/update_manager.rb
@@ -26,7 +26,7 @@ module Arel
         @head.values = [values]
       else
         @head.values = values.map { |column,value|
-          Nodes::Equality.new(
+          Nodes::Assignment.new(
             Nodes::UnqualifiedColumn.new(column),
             value
           )
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index f70cae9430..8638bf43c3 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -149,13 +149,24 @@ module Arel
         "#{visit o.left} OR #{visit o.right}"
       end
 
-      def visit_Arel_Nodes_Equality o
+      def visit_Arel_Nodes_Assignment o
         right = o.right
-        # FIXME: maybe we should visit NilClass?
+
         right = right.nil? ? 'NULL' : visit(right)
         "#{visit o.left} = #{right}"
       end
 
+      def visit_Arel_Nodes_Equality o
+        right = o.right
+
+        # FIXME: maybe we should visit NilClass?
+        if right.nil?
+          "#{visit o.left} IS NULL"
+        else
+          "#{visit o.left} = #{visit right}"
+        end
+      end
+
       def visit_Arel_Nodes_UnqualifiedColumn o
         "#{quote_column_name o.name}"
       end
-- 
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