Thanks Tom. It's a strange one for sure. Hopefully AWS support will shed some light on it. I will clarify too that this is the regular RDS Postgres version and not their other Aurora Postgres service. I suspect the Aurora Postgres probably differs from the community version by quite a bit, but I'm unsure how much their regular Postgres offering differs, if at all.
Thanks, Chris On Mon, Oct 18, 2021 at 8:05 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Chris Williams <cswilli...@gmail.com> writes: > > We have a script that runs a pg_dump off of an RDS PG13.3 replica several > > times per day. We then load this dump using pg_restore into another > > postgres RDS db in another AWS account, scrub some of the data, and then > > take a snapshot of it. > > Hmm ... I'm fairly sure that RDS Postgres is not Postgres at this level > of detail. The info I've been able to find about their replication > mechanism talks about things like "eventually consistent reads", which > is not something community Postgres deals in. > > In particular, what I'd expect from the community code is that a replica > could see a sequence as being *ahead* of the value that you might expect > from looking at related tables; but never behind. (Also, that statement > is true regardless of whether you are doing parallel dump.) And > non-sequence tables should always be consistent, period. > > So I'm suspicious that this is an RDS-specific effect, and thus that > you should consult Amazon support first. If they say "no, it's Postgres > all the way down", then we need to look closer. > > regards, tom lane >
