On Thu, Aug 15, 2024 at 09:49:04AM +0200, Jakub Wartak wrote: > On Wed, Aug 7, 2024 at 4:18 PM Greg Sabino Mullane <htamf...@gmail.com> wrote: > > > > On Wed, Aug 7, 2024 at 4:43 AM Michael Banck <mba...@gmx.net> wrote: > >> > >> I think the last time we dicussed this the consensus was that > >> computational overhead of computing the checksums is pretty small for > >> most systems (so the above change seems warranted regardless of whether > >> we switch the default), but turning on wal_compression also turns on > >> wal_log_hints, which can increase WAL by quite a lot. Maybe this is > [..] > > > > > > Yeah, that seems something beyond this patch? Certainly we should > > mention wal_compression in the release notes if the default changes. > > I mean, I feel wal_log_hints should probably default to on as well, > > but I've honestly never really given it much thought because my > > fingers are trained to type "initdb -k". I've been using data > > checksums for roughly a decade now. I think the only time I've NOT > > used checksums was when I was doing checksum overhead measurements, > > or hacking on the pg_checksums program. > > Maybe I don't understand something, but just to be clear: > wal_compression (mentioned above) is not turning wal_log_hints on, > just the wal_log_hints needs to be on when using data checksums > (implicitly, by the XLogHintBitIsNeeded() macro). I suppose Michael > was thinking about the wal_log_hints earlier (?)
Uh, I am pretty sure I meant to say "turning on data_checksums als turns on wal_log_hints", sorry about the confusion. I guess the connection is that if you turn on wal_lot_hints (either directly or via data_checksums) then the number FPIs goes up (possibly signficantly), and enabling wal_compression could (partly) remedy that. But I agree with Greg that such a discussion is probably out-of-scope for this default change. Michael
