The migration raises first unless chain_moved names builds, rollouts and assignments for every kind that holds rows, and unless pending_assignment holds no open or unanswered row; then it drops build_request, build, batched_merge, release_plan, pending_assignment, assignment, raise_assignment_generation(), node.sent_builds and chain_moved. build_gate stays.
SentBuilds answers from the keys of the node's assignments that name a commit, known when the node was sent anything and no key says its commit unknown. A send that names its builds writes the commit, build and rollout on each carried module's key (a module nothing assigns gets a standing key marked pulled-in, never a state) and clears what every other key of the node named; a send by hand writes sent-unknown, a time, on every key and clears their commits. A failed write of these fails the record of the send. node.sent_builds is no longer written. The plan pass ends a pulled-in key only when no send carries it.
jschoubben