adding not equal node, column names are expected to be symbols

lib/arel/attributes/attribute.rb

 module Arel
   module Attributes
     class Attribute < Struct.new :relation, :name, :column
+      def not_eq other
+        Nodes::NotEqual.new self, other
+      end
+
       def eq other
         Nodes::Equality.new self, other
       end

lib/arel/compatibility/wheres.rb

@@ -8,6 +8,10 @@ module Value # :nodoc:
         def value
           visitor.accept self
         end
+
+        def name
+          super.to_sym
+        end
       end
 
       def initialize engine, collection

lib/arel/nodes.rb

 require 'arel/nodes/binary'
 require 'arel/nodes/equality'
+require 'arel/nodes/not_equal'
 require 'arel/nodes/assignment'
 require 'arel/nodes/or'
 require 'arel/nodes/and'

lib/arel/nodes/not_equal.rb

+module Arel
+  module Nodes
+    class NotEqual < Arel::Nodes::Binary
+    end
+  end
+end

lib/arel/nodes/table_alias.rb

@@ -12,7 +12,7 @@ def initialize name, relation
       end
 
       def [] name
-        name = name.to_s
+        name = name.to_sym
         columns.find { |column| column.name == name }
       end
     end

lib/arel/table.rb

@@ -73,12 +73,12 @@ def having expr
 
     def columns
       @columns ||= @engine.connection.columns(@name, "#{@name} Columns").map do |column|
-        Attributes.for(column).new self, column.name, column
+        Attributes.for(column).new self, column.name.to_sym, column
       end
     end
 
     def [] name
-      name = name.to_s
+      name = name.to_sym
       columns.find { |column| column.name == name }
     end
   end

lib/arel/visitors/to_sql.rb

@@ -159,7 +159,6 @@ def visit_Arel_Nodes_Assignment o
       def visit_Arel_Nodes_Equality o
         right = o.right
 
-        # FIXME: maybe we should visit NilClass?
         if right.nil?
           "#{visit o.left} IS NULL"
         else
@@ -167,6 +166,16 @@ def visit_Arel_Nodes_Equality o
         end
       end
 
+      def visit_Arel_Nodes_NotEqual o
+        right = o.right
+
+        if right.nil?
+          "#{visit o.left} IS NOT NULL"
+        else
+          "#{visit o.left} != #{visit right}"
+        end
+      end
+
       def visit_Arel_Nodes_UnqualifiedColumn o
         "#{quote_column_name o.name}"
       end

spec/arel/attributes/attribute_spec.rb

@@ -3,6 +3,31 @@
 module Arel
   module Attributes
     describe 'attribute' do
+      describe '#not_eq' do
+        it 'should create a NotEqual node' do
+          relation = Table.new(:users)
+          relation[:id].not_eq(10).should be_kind_of Nodes::NotEqual
+        end
+
+        it 'should generate != in sql' do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_eq(10)
+          mgr.to_sql.should be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" != 10
+          }
+        end
+
+        it 'should handle nil' do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_eq(nil)
+          mgr.to_sql.should be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" IS NOT NULL
+          }
+        end
+      end
+
       describe '#gt' do
         it 'should create a GreaterThan node' do
           relation = Table.new(:users)

spec/arel/table_spec.rb

@@ -120,7 +120,7 @@ module Arel
       it 'returns a list of columns' do
         columns = @relation.columns
         check columns.length.should == 2
-        columns.map { |x| x.name }.sort.should == %w{ name id }.sort
+        columns.map { |x| x.name.to_s }.sort.should == %w{ name id }.sort
       end
     end
 
@@ -136,7 +136,7 @@ module Arel
       describe 'when given a', Symbol do
         it "manufactures an attribute if the symbol names an attribute within the relation" do
           column = @relation[:id]
-          check column.name.should == 'id'
+          check column.name.should == :id
           column.should be_kind_of Attributes::Integer
         end
       end