sql - Calculate BLOB size using triggers in mysql -

i'm trying calculate blob size of table using triggers.

this code

create trigger 'test' before insert on 'mytable' each row set new.blobsize = lenght(new.blobfile); 

but recive following error

function dbname.lenght not exist 

any advice?

the function after length(). note is spelled th, not ht (which have):

create trigger 'test' before insert on 'mytable' each row set new.blobsize = length(new.blobfile);