Function transform_recursive 

pub fn transform_recursive<F>(
    expr: Expression,
    transform_fn: &F,
) -> Result<Expression>
where
    F: Fn(Expression) -> Result<Expression>,

Applies a transform function bottom-up through an entire expression tree.

The public entrypoint uses an explicit task stack for the recursion-heavy shapes that dominate deeply nested SQL (nested SELECT/FROM/SUBQUERY chains, set-operation trees, and common binary/unary expression chains). Less common shapes currently reuse the reference recursive implementation so semantics stay identical while the hot path avoids stack growth.