Re: logical decoding and replication of sequences, take 2

On 02.04.23 19:46, Tomas Vondra wrote:
> OK, I took a stab at this, see the attached 0007 patch which bumps the
> protocol version, and allows the subscriber to specify "sequences" when
> starting the replication, similar to what we do for the two-phase stuff.
> 
> The patch essentially adds 'sequences' to the replication start command,
> depending on the server version, but it can be overridden by "sequences"
> subscription option. The patch is pretty small, but I wonder how much
> smarter this should be ...

I think this should actually be much simpler.

All the code needs to do is:

- Raise protocol version (4->5)  (Your patch does that.)

- pgoutput_sequence() checks whether the protocol version is >=5 and if 
not it raises an error.

- Subscriber uses old protocol if the remote end is an older PG version. 
  (Your patch does that.)

I don't see the need for the subscriber to toggle sequences explicitly 
or anything like that.