src/Pure/Admin/build_log.scala

       val columns1 = table1.columns.tail.map(_.apply(table1))
       val (columns, from) =
         if (ml_statistics) {
           val columns = columns1 ::: List(Data.ml_statistics(table2))
           val join =
-            table1.toString + SQL.join_outer + table2 + " ON " +
+            table1.ident + SQL.join_outer + table2.ident + " ON " +
               SQL.and(
                 Data.log_name(table1).ident + " = " + Data.log_name(table2).ident,
                 Data.session_name(table1).ident + " = " + Data.session_name(table2).ident)
           (columns, SQL.enclose(join))
         }