Required. A per-transaction sequence number used to identify this request. This field makes each request idempotent such that if the request is received multiple times, at most one succeeds. The sequence number must be monotonically increasing within the transaction. If a request arrives for the first time with an out-of-order sequence number, the transaction might be aborted. Replays of previously handled requests yield the same response as the first execution.

Optional. If set to true, this request marks the end of the transaction. After these statements execute, you must commit or abort the transaction. Attempts to execute any other requests against this transaction (including reads and queries) are rejected. Setting this option might cause some error reporting to be deferred until commit time (for example, validation of unique constraints). Given this, successful execution of statements shouldn't be assumed until a subsequent Commit call completes successfully.