What locks does a REVOKE ALL PRIVILEGES ON a PostgreSQL table require?

Question

What locks does a REVOKE ALL PRIVILEGES ON a PostgreSQL table require?

Specifically, could it get blocked by a long running ALTER TABLE which adds a column to the table?

Answer 1

REVOKE and GRANT don't take any lock on the table itself, but they modify the table's relacl in pg_class, so they need a NO KEY UPDATE lock on that row.

This will conflict with all other operations that also modify the table metadata, in particular ALTER TABLE.