> >>Uh, what if a transaction modifies page 0 and page 1 of the same table
> >>--- don't those pages have the same LSN. > > > >No, because WAL being a physical change log, each page gets its own > >WAL record with its own LSN. > > > > What if you have wal_log_hints=off? AFAIK that won't change the page LSN. > > Alvaro suggested elsewhere that we require checksums for these, which > would also force wal_log_hints to be on, and therefore the LSN would > change. Yes, it sounds like the agreement was LSN is unique when wal_log_hints is on. I don't know enough about the internals to know if pg_class.oid is also needed or not. Ryan On Wed, Jul 10, 2019 at 6:07 PM Bruce Momjian <br...@momjian.us> wrote: > On Thu, Jul 11, 2019 at 12:18:47AM +0200, Tomas Vondra wrote: > > On Wed, Jul 10, 2019 at 06:04:30PM -0400, Stephen Frost wrote: > > > Greetings, > > > > > > * Tomas Vondra (tomas.von...@2ndquadrant.com) wrote: > > > > On Wed, Jul 10, 2019 at 04:11:21PM -0400, Alvaro Herrera wrote: > > > > >On 2019-Jul-10, Bruce Momjian wrote: > > > > > > > > > >>Uh, what if a transaction modifies page 0 and page 1 of the same > table > > > > >>--- don't those pages have the same LSN. > > > > > > > > > >No, because WAL being a physical change log, each page gets its own > > > > >WAL record with its own LSN. > > > > > > > > > > > > > What if you have wal_log_hints=off? AFAIK that won't change the page > LSN. > > > > > > Alvaro suggested elsewhere that we require checksums for these, which > > > would also force wal_log_hints to be on, and therefore the LSN would > > > change. > > > > > > > Oh, I see - yes, that would solve the hint bits issue. Not sure we want > > to combine the features like this, though, as it increases the costs of > > TDE. But maybe it's the best solution. > > Uh, why can't we just force log_hint_bits for encrypted tables? Why > would we need to use checksums as well? > > Why is page-number not needed in the nonce? Because it is duplicative > of the LSN? Can we use just LSN? Do we need pg_class.oid too? > > -- > Bruce Momjian <br...@momjian.us> http://momjian.us > EnterpriseDB http://enterprisedb.com > > + As you are, so once was I. As I am, so you will be. + > + Ancient Roman grave inscription + >
