isAuthoritative

Whether the candidates alone are a superset of the answer.

False when a segment is uncovered, and false when the store holds documents that are not in a segment at all. A memtable has no sidecar and never will — there is no per-segment unit to attach one to — so a store with unflushed writes always needs the scan.

The check is made before the live segment set is read, and the order is what makes this sound rather than merely likely: anything landing in a memtable afterwards carries a sequence above this snapshot's and is invisible to it, and anything the snapshot can see was already in a segment the live set then named.