Single‑transaction schema migration versus compensating transaction: trade‑off for rollback safety after a required‑field addition
When a FaunaDB FQL transaction modifies a document and concurrently applies a schema change that adds a required field, the resulting state after a rollback depends on how the engine treats non‑data operations within a serializable transaction. The precise goal is to determine whether the rollback reverts the document to its pre‑change schema or leaves the n