Anyway, new patch, which adds SET TABLESPACE to REINDEX is attached and this functionality seems really useful, so I will be very appreciate if someone will take a look on it.
* There are NOWAIT option in alter index, is there a reason not to have similar option here?
* SET TABLESPACE command is not documented
* There are multiple checking for whether the relation is temporary tables of other sessions, one in check_relation_is_movable and other independently
*+ char *tablespacename;
calling it new_tablespacename will make it consistent with other places