sequence

PostgreSQL native reservations

PostgreSQL 10+ native catalogs resolve SERIAL, GENERATED BY DEFAULT/ALWAYS identity, direct nextval defaults (including unowned sequences), and an explicit mapped sequence. The server resolves identifiers and search_path. Non-integer columns, missing generators, ambiguous/transformed defaults without an explicit authority, cycling sequences and out-of-column-range values have shape-specific diagnostics. No source schema or trigger is changed.

insert.Service.ReserveSequence returns sink.Reservation.Values: actual values returned by nextval, in returned order. Backend caches and concurrent calls may produce [2,3,7], descending values, or values lower than an earlier reservation. No arithmetic range or monotonic last-value inference is valid for this API. The old scalar NextSequence API diagnoses this distinction before consuming values. Native insert assignment consumes the same exact-value owner.

nextval values are not reclaimed by rollback. Cancellation/exhaustion can consume values without returning a successful batch; records are not assigned partial batches. No MAX, setval, sequence restart, allocator table, source INSERT or extra caller connection is used. A supplied transaction remains caller-owned; normal PostgreSQL statement-error transaction-abort semantics still apply.

Native PostgreSQL inserts use OVERRIDING SYSTEM VALUE when materializing mapped identity values, allowing preallocated values for GENERATED ALWAYS columns. The clause is ignored by PostgreSQL for columns where it is inapplicable. RETURNING rows are consumed directly and their errors are preserved.