On Sat, May 4, 2024 at 7:36 AM Joe Conway <m...@joeconway.com> wrote: > > On 5/3/24 11:44, Peter Eisentraut wrote: > > On 03.05.24 16:13, Tom Lane wrote: > >> Peter Eisentraut <pe...@eisentraut.org> writes: > >>> On 30.04.24 19:29, Tom Lane wrote: > >>>> Also, the bigger picture here is the seeming assumption that "if > >>>> we change pg_trgm then it will be safe to replicate from x86 to > >>>> arm". I don't believe that that's a good idea and I'm unwilling > >>>> to promise that it will work, regardless of what we do about > >>>> char signedness. That being the case, I don't want to invest a > >>>> lot of effort in the signedness issue. Option (1) is clearly > >>>> a small change with little if any risk of future breakage. > >> > >>> But note that option 1 would prevent some replication that is currently > >>> working. > >> > >> The point of this thread though is that it's working only for small > >> values of "work". People are rightfully unhappy if it seems to work > >> and then later they get bitten by compatibility problems. > >> > >> Treating char signedness as a machine property in pg_control would > >> signal that we don't intend to make it work, and would ensure that > >> even the most minimal testing would find out that it doesn't work. > >> > >> If we do not do that, it seems to me we have to buy into making > >> it work. That would mean dealing with the consequences of an > >> incompatible change in pg_trgm indexes, and then going through > >> the same dance again the next time(s) similar problems are found. > > > > Yes, that is understood. But anecdotally, replicating between x86-64 arm64 > > is > > occasionally used for upgrades or migrations. In practice, this appears to > > have > > mostly worked. If we now discover that it won't work with certain index > > extension modules, it's usable for most users. Even if we say, you have to > > reindex everything afterwards, it's probably still useful for these > > scenarios. > > +1
+1 How about extending amcheck to support GIN and GIst indexes so that it can detect potential data incompatibility due to changing 'char' to 'unsigned char'? I think these new tests would be useful also for users to check if they really need to reindex indexes due to such changes. Also we fix pg_trgm so that it uses 'unsigned char' in PG18. Users who upgraded to PG18 can run the new amcheck tests on the primary as well as the standby. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com
