fn lineage_literal(
plan: &LogicalPlan,
output_idx: usize,
) -> Option<&ScalarValue>Expand description
Resolves a literal when every row carries the same value at output_idx.
Read-only: the literal is folded into the assignment above, so nodes that drop, reorder or deduplicate rows can be traversed — none of them changes the value a surviving row carries, and folding above them leaves their keys on the original strings.