On Mon, Jul 15, 2024 at 04:03:13PM -0400, Robert Haas wrote: > On Mon, Jul 15, 2024 at 2:47 PM Nathan Bossart <nathandboss...@gmail.com> > wrote: >> My understanding is that the correctness of this GUC check hook depends on >> wal_level being a PGC_POSTMASTER GUC. The check hook would always return >> true during startup, and there'd be an additional cross-check in >> PostmasterMain() that would fail startup if necessary. After that point, >> we know that wal_level cannot change, so the GUC check hook for >> summarize_wal can depend on wal_level. If it fails, my expectation would >> be that the server would just ignore that change and continue. > > But how do you know that, during startup, the setting for > summarize_wal is processed after the setting for wal_level?
You don't, but the GUC check hook should always return true when summarize_wal is processed first. We'd rely on the PostmasterMain() check to fail in that case. -- nathan
