Added TODO comments

sql/opt_subselect.cc

@@ -4216,6 +4216,8 @@ bool JOIN::optimize_unflattened_subqueries()
     Currently there are only two possible startup functions, so we have them
     both here inside if (...) branches. In future we could switch to function
     pointers.
+
+  TODO: consider moving this together with JOIN_TAB::preread_init
   
   RETURN 
     NESTED_LOOP_OK - OK

sql/sql_select.cc

@@ -9479,6 +9479,8 @@ double JOIN_TAB::scan_time()
 /**
   Initialize the join_tab before reading.
   Currently only derived table/view materialization is done here.
+
+  TODO: consider moving this together with join_tab_execution_startup
 */
 bool JOIN_TAB::preread_init()
 {