On Tue, Jan 12, 2021 at 01:44:05PM -0500, Stephen Frost wrote:
> * Bruce Momjian (bruce@momjian.us) wrote:
> > Well, we have eight unused bits in the IV, so we could just increment
> > that for every hint bit change that uses the same LSN, and then force a
> > dummy WAL record when that 8-bit counter overflows --- that seems
> > simpler than logging hint bits.
>
> Sure, as long as we have a place to store that information.. We need to
> have the full IV available when we go to decrypt the page.
Oh, yeah, we would need that counter recorded since previously the IV
was made up of already-recorded information, i.e., the page LSN and page
number. However, the reason don't WAL-log hint bits always is because
we can afford to lose them, but in this case, any counter we need to
store will need to be WAL logged since we can't affort to lose that
counter value for decryption --- that gets us back to WAL-logging
something during hint bit changes. :-(
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
The usefulness of a cup is in its emptiness, Bruce Lee