adding a case_sensitive_modifier for forcing comparisons to be case sensitive

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -203,6 +203,10 @@ def rollback_to_savepoint
       def release_savepoint
       end
 
+      def case_sensitive_modifier(node)
+        node
+      end
+
       def current_savepoint_name
         "active_record_#{open_transactions}"
       end

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -528,6 +528,11 @@ def primary_key(table)
       def case_sensitive_equality_operator
         "= BINARY"
       end
+      deprecate :case_sensitive_equality_operator
+
+      def case_sensitive_modifier(node)
+        Arel::Nodes::Bin.new(node)
+      end
 
       def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
         where_sql

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -655,6 +655,11 @@ def primary_key(table)
       def case_sensitive_equality_operator
         "= BINARY"
       end
+      deprecate :case_sensitive_equality_operator
+
+      def case_sensitive_modifier(node)
+        Arel::Nodes::Bin.new(node)
+      end
 
       def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
         where_sql

activerecord/lib/active_record/validations/uniqueness.rb

@@ -59,6 +59,7 @@ def build_relation(klass, table, attribute, value) #:nodoc:
         if !options[:case_sensitive] && column.text?
           relation = table[attribute].matches(value)
         else
+          value    = klass.connection.case_sensitive_modifier(value)
           relation = table[attribute].eq(value)
         end