Function render_columns 

pub fn render_columns<Q, T>(
    columns: &[PlannedColumn],
    quote: Q,
    ty: T,
) -> String
where
    Q: Fn(&str) -> String,
    T: Fn(SqlBaseType) -> &'static str,

Render a CREATE TABLE column list, given a dialect’s type mapper and identifier quoter.

Kept separate from plan_columns so a sink whose CREATE TABLE needs extra clauses (a primary key, a partition spec, an engine) composes this into its own statement rather than fighting a one-size template.