HistoricalFanout
source: marts: marts.orders.flatten[0].via
flatten step joins entity 'customer' through relationship 'order_of_customer' (many_to_one), and 'customer' is declared scd: type2 — without an anchor the emitted join carries no validity predicate, so it matches every version of each 'customer' key and each base row is multiplied by that key's version count. The declared cardinality is a claim about the domain; the relation holds one row per version (S-0040/D-1). Fix: declare an anchor — as_of: <a date or timestamp column of the base> — to read the dimension as of that instant, or declare the entity scd: type1
