On Wed, 2024-02-14 at 23:52 +0100, Hannes Erven wrote: > when "SELECT .. WHERE .. FOR NO KEY UPDATE" is used synchronize access, > and the transaction holding the lock completes, how does PostgreSQL > decide /which one/ of multiple waiting transactions will the lock be > granted to next? > > In my testing (on Ubuntu 16.1-1.pgdg20.04+1, 64bit) with a real-world > application (that acquires multiple locks on a number of relations) it > seems that it is always the transaction that attempted to lock _last_ ... ? > I thought that would most probably be random, or if it was not, the > order would have been explained in the docs?
Transactions queue behind a lock, and they get the lock in a "first come, first served" order. Yours, Laurenz Albe
