UTF8 test query

gistfile1.txt

select * from yourtable t
 where encode(convert_to(t::text,'SQL_ASCII'),'hex')
       !~ '(?x)
           ^(?:(?:[0-7][0-9a-f])
              |(?:(?:c[2-9a-f]|d[0-9a-f])
                 |e0[ab][0-9a-f]
                 |ed[89][0-9a-f]
                 |(?:(?:e[1-9abcef])
                    |f0[9ab][0-9a-f]
                    |f[1-3][89ab][0-9a-f]
                    |f48[0-9a-f]
                  )[89ab][0-9a-f]
                )[89ab][0-9a-f]
             )*$';