Robert Haas <robertmh...@gmail.com> wrote: > On Mon, Aug 5, 2019 at 8:44 PM Bruce Momjian <br...@momjian.us> wrote: > > Right. The 8k page LSN changes each time the page is modified, and the > > is part of the page nonce. > > What about hint bit changes? > > I think even with wal_log_hints=on, it's not the case that *every* > change to hint bits results in an LSN change.
Change to hint bits does not result in LSN change in the case I described here https://www.postgresql.org/message-id/28452.1572443058%40antos but I consider this a bug (BTW, I discovered this problem when thinking about the use of LSN as encryption IV). Do you mean any other case? If LSN does not get changed, then the related full-page image WAL record is not guaranteed to be on disk during crash recovery. Thus if page checksum is invalid due to torn-page write, there's now WAL record to fix the page. -- Antonin Houska Web: https://www.cybertec-postgresql.com
