On Sat, Sep 12, 2026 at 11:05 PM Noah Misch <[email protected]> wrote: > On Mon, Sep 07, 2026 at 06:22:22PM +0300, Alexander Korotkov wrote: > > 0002 is patch for FSM readme to highlight this aspect > > > > I'm going to push (and backpatch) 0001. 0002 needs review. > > > Subject: [PATCH v1 2/2] Say in the FSM README why its hint writes still need > > full page images > > > +That RBM_ZERO_ON_ERROR is a property of this directory, not of the FSM fork > > +itself. The files themselves are ordinary relation files, and plenty of > > code > > +outside freespace.c reads them and does verify checksums: > > +RelationCopyStorage(), which ALTER TABLE ... SET TABLESPACE runs over every > > +fork; the read stream in RelationCopyStorageUsingBuffer(), used by > > +CREATE DATABASE ... STRATEGY = wal_log; and the checksum verification in > > base > > +backups and in pg_checksums. The last two are the reason this cannot > > simply be > > +relaxed: an external verification tool has no way to tell a tear that we > > +consider harmless from one caused by failing storage, so making it accept > > +the former blinds it to the latter. > > One could relax the "last two" by having those tools skip checksum > verification for *_fsm files, so let's not claim it's infeasible. It's true > that this could miss failing-storage evidence that coincidentally landed in > FSM, but accepting that could be the right thing someday. Other than that, I > agree with this README change. Thanks.
I've corrected that paragraph. I'm going to push this to master if no objections. ------ Regards, Alexander Korotkov Supabase
v2-0001-Say-in-the-FSM-README-why-its-hint-writes-still-n.patch
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