Function single_evaluation_projection_expr_allowed 

fn single_evaluation_projection_expr_allowed(
    expr: &Expr,
    projection: &Projection,
) -> bool

This whitelist assumes the planner preserves time-index and series identity; it is not a proof that an arbitrary plan does so.

Identity projections preserve the selected samples. Only the planner’s named seconds/milliseconds-to-milliseconds casts are accepted; a microsecond or nanosecond cast could collapse a future sample onto the evaluation boundary.