On Fri, Mar 29, 2019 at 4:30 PM Stephen Frost <sfr...@snowman.net> wrote:
> Greetings, > > * Magnus Hagander (mag...@hagander.net) wrote: > > On Thu, Mar 28, 2019 at 10:19 PM Tomas Vondra < > tomas.von...@2ndquadrant.com> > > wrote: > > > > > On Thu, Mar 28, 2019 at 01:11:40PM -0700, Andres Freund wrote: > > > >Hi, > > > > > > > >On 2019-03-28 21:09:22 +0100, Michael Banck wrote: > > > >> I agree that the current patch might have some corner-cases where it > > > >> does not guarantee 100% accuracy in online mode, but I hope the > current > > > >> version at least has no more false negatives. > > > > > > > >False positives are *bad*. We shouldn't integrate code that has them. > > > > > > > > > > Yeah, I agree. I'm a bit puzzled by the reluctance to make the online > mode > > > communicate with the server, which would presumably address these > issues. > > > Can someone explain why not to do that? > > > > I agree that this effort seems better spent on fixing those issues there > > (of which many are the same), and then re-use that. > > This really seems like it depends on which of the options we're talking > about.. Connecting to the server and asking what the current insert > point is, so we can check that the LSN isn't completely insane, seems > reasonable, but at least one option being discussed was to have > pg_basebackup actually *lock the page* (even if just for I/O..) and then > re-read it, and having an external tool doing that instead of the > backend seems like a whole different level to me. That would involve > having an SQL function for "lock this page against I/O" and then another > for "unlock this page", wouldn't it? > Right. But what if we just added a flag to the BASE_BACKUP command in the replication protocol that said "meh, I really just want to verify the checksums, so please send the data to devnull and only feed me regular status updates on this connection"? -- Magnus Hagander Me: https://www.hagander.net/ <http://www.hagander.net/> Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>
