FlatLineage

The fingerprints of the flat view's definitions that writers created it with, oldest first, as its comment keeps them (wow-sink-flat:<fingerprint>,<fingerprint>): the last is the view's definition.

During a rolling upgrade, instances of two versions start and restart in turn, each creating the view of its own state schema. A writer replaces the view only when its own fingerprint is not in the lineage yet, a newer definition than every one before it; one whose fingerprint is there but not last was replaced by a newer writer and leaves the view as it is. The lineage keeps the last MAX fingerprints; a view without one (created by an earlier Wow, or by an operator) has an empty lineage, which the first writer replaces.