Function equality_ids_for_indices 

fn equality_ids_for_indices(
    current_schema: &Schema,
    materialize_arrow_schema: &Schema,
    equality_indices: &[usize],
) -> Result<Vec<i32>>

Resolve Materialize key column indexes to Iceberg top-level field IDs.

Iceberg field IDs are assigned recursively, so a top-level column’s field ID is not necessarily column_index + 1 once nested fields are present.