Why GRANT UPDATE on SEQUENCE in PostgreSQL

Question

I have seen postgresql allowing users to Grant update on a sequence. But never seen any update query on the sequence. Sequence values are usually changed using ALTER SEQUENCE command. I understand the need for GRANT USAGE and GRANT SELECT on sequences. But what exactly does a GRANT UPDATE on a sequence lets you do in PostgreSQL.

Answer 1

The documentation says:

nextval ( regclass ) → bigint

[...]
This function requires USAGE or UPDATE privilege on the sequence.

---

setval ( regclass, bigint [, boolean ] ) → bigint

[...]
This function requires UPDATE privilege on the sequence.