Function ltrim 

pub fn ltrim<'a, V, E>(expr: E) -> SQLExpr<'a, V, Text, E::Nullable, Scalar>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: Textual,

LTRIM - removes leading whitespace.

Preserves the nullability of the input expression.