Function synth_cell 

pub fn synth_cell(scalar_type: &SqlScalarType, i: u64, pad: usize) -> Cell

A deterministic synthetic value for a column of scalar_type at row index i.

pad widens text columns so callers can target a byte budget. Each value is a function of i, so a row is distinct per i as long as the schema has at least one wide-enough column (int, text, or bytes); an all-bool schema would collide. Unsupported types panic — schema construction rejects them first.