Function plan_row_idx_expression 

pub fn plan_row_idx_expression(
    expression: BoundExpression,
    child: PlanRef,
) -> VortexResult<PlanRef>

Plans an expression over a data source and its global row-index domain.

Expressions that only use data bypass the row-index source, expressions that only use #row_idx bypass child, and mixed expressions combine independently planned branches with a PackPlan. The file row offset is supplied by the execution row domain.