Function boundaries_strictly_monotonic 

async fn boundaries_strictly_monotonic<Q>(
    conn: &mut Q,
    boundaries: &[String],
    charset: &str,
    collation: &str,
) -> Result<bool, TransientError>
where
    Q: Queryable,

Whether boundaries are strictly increasing under collation. The half-open PK ranges only partition the table without gaps or overlaps when this holds. The boundaries are already SQL literals (from QUOTE()); each is coerced to charset/collation so the comparison uses the same collation as the column, matching the read predicates. Fewer than two boundaries are trivially monotonic.