use these sqls:
create table t(a text);
insert into t values('a');
select lp,lp_len,t_data from heap_page_items(get_raw_page('t',0));
lp | lp_len | t_data
----+--------+--------
1 | 26 | \x0561
as you can see, the 61 is 'a', so what's the 05??? strange.
