Il giorno mar 16 feb 2021 alle ore 10:51 Jehan-Guillaume de Rorthais < j...@dalibo.com> ha scritto:
> On Mon, 15 Feb 2021 18:55:14 +0100 > Paolo Saudin <paolosau...@gmail.com> wrote: > > > Hi all, > > I have two servers, a primary and a secondary one with a streaming > replica > > setup. > > Today I noticed that some sequences are not lined-up, the replica ones > are > > well ahead, while the records number is the same. How is it possible? > > This is because sequences are not WAL logged on every nextval() call, but > by > batch of sequence cache+32 values. As standbys are fed with WAL stream from > primary, their sequences appears jump, then stall, then jump, etc. > > See: > > https://git.postgresql.org/cgit/postgresql.git/tree/src/backend/commands/sequence.c?id=f672df5fdd22dac14c98d0a0bf5bbaa6ab17f8a5#n52 > > > https://git.postgresql.org/cgit/postgresql.git/tree/src/backend/commands/sequence.c?id=f672df5fdd22dac14c98d0a0bf5bbaa6ab17f8a5#n661 > > I'm not sure if this is documented somewhere... ? > Thank you very much! So in case the primary server crashes, and the backup one gets live, it will eventually have different sequences. I suppose there is no way to avoid this, isnt'it? Paolo
