Constant WRITER_LOCK_KEY 

pub const WRITER_LOCK_KEY: i64 = 0x0067_776b_0077_7231;

The advisory-lock key for “this database’s kernel writer”.

Advisory locks share one namespace per database, so the key is a constant anything else in this database must avoid. It spells gwk in the high bytes and wr1 in the low ones, which makes an unexpected holder identifiable in pg_locks instead of anonymous.