On 18 April 2016 at 12:43, Michael Paquier <michael.paqu...@gmail.com> wrote:
> On Sat, Apr 16, 2016 at 5:37 AM, Alvaro Herrera > <alvhe...@2ndquadrant.com> wrote: > > Andres Freund wrote: > >> On 2016-04-15 15:26:17 -0400, Tom Lane wrote: > >> > I think the bottom line is that we misdesigned the WAL representation > >> > by assuming that this sort of info could always be piggybacked on a > >> > transaction commit record. It's time to fix that. > >> > >> I think we got to piggyback it onto a commit record, as long as there's > >> one. Otherwise it's going to be more complex (queuing messages when > >> reading an inval record) and slower (more wal records). I can easily > >> develop a patch for that, the question is what we do on the back > >> branches... > > > > We have introduced new wal records in back branches previously -- > > nothing new (c.f. 8e9a16ab8f7f0e5813644975cc3f336e5b064b6e). The user > > just needs to make sure to upgrade the standbys first. If they don't, > > they would die upon replay of the first such record, which they can take > > as an indication that they need to be upgraded; the standby is down for > > some time, but there is no data loss or corruption. > > Yeah, introducing a new WAL record to address this issue in > back-branches would not be an issue, and that's what we should do. For > HEAD, let's add that in the commit record. > (non-reply just because of travel) OK, I'll write up a patch today to fix, with a view to backpatching. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
