Function lpad_fill 

pub fn lpad_fill(s: &str, length: i32, fill: &str, writer: &mut impl Write)

Extends the string to the specified length by prepending the characters fill. If the string is already longer than the specified length, it is truncated on the right.

Example

query T
select lpad('hi', 5, 'xy');
----
xyxhi

query T
select lpad('hi', 5, '');
----
hi