diff -r e13aa4786a72 -r 1faff41593df server/sources/rql2sql.py
--- a/server/sources/rql2sql.py	Fri Jun 18 15:41:39 2010 +0200
+++ b/server/sources/rql2sql.py	Fri Jun 18 18:14:55 2010 +0200
@@ -1096,7 +1096,8 @@
         operator = mexpr.operator
         try:
             if mexpr.operator == '+' and mexpr.get_type(self._state.solution, self._args) == 'String':
-                operator = '||'
+                return '(%s)' % self.dbhelper.sql_concat_string(lhs.accept(self),
+                                                                rhs.accept(self))
         except CoercionError:
             pass
         return '(%s %s %s)'% (lhs.accept(self), operator, rhs.accept(self))