Re: Perform streaming logical transactions by background workers and parallel apply

On Fri, Jul 1, 2022 at 12:13 PM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> ======
>
> 1.2 doc/src/sgml/protocol.sgml - Protocol constants
>
> Previously I wrote that since there are protocol changes here,
> shouldn’t there also be some corresponding LOGICALREP_PROTO_XXX
> constants and special checking added in the worker.c?
>
> But you said [1 comment #6] you think it is OK because...
>
> IMO, I still disagree with the reply. The fact is that the protocol
> *has* been changed, so IIUC that is precisely the reason for having
> those protocol constants.
>
> e.g I am guessing you might assign the new one somewhere here:
> --
> server_version = walrcv_server_version(LogRepWorkerWalRcvConn);
> options.proto.logical.proto_version =
> server_version >= 150000 ? LOGICALREP_PROTO_TWOPHASE_VERSION_NUM :
> server_version >= 140000 ? LOGICALREP_PROTO_STREAM_VERSION_NUM :
> LOGICALREP_PROTO_VERSION_NUM;
> --
>
> And then later you would refer to this new protocol version (instead
> of the server version) when calling to the apply_handle_stream_abort
> function.
>
> ======
>

One point related to this that occurred to me is how it will behave if
the publisher is of version >=16 whereas the subscriber is of versions
<=15? Won't in that case publisher sends the new fields but
subscribers won't be reading those which may cause some problems.

> ======
>
> 1.5 src/backend/commands/subscriptioncmds.c
>
> + /*
> + * If no parameter given, assume "true" is meant.
> + */
>
> Previously I suggested an update for this comment, but it was rejected
> [1 comment #12] saying you wanted consistency with defGetBoolean.
>
> Sure, that is one point of view. Another one is that "two wrongs don't
> make a right". IIUC that comment as it currently stands is incorrect
> because in this case there *is* a parameter given - it is just the
> parameter *value* that is missing.
>

You have a point but if we see this function in the vicinity then the
proposed comment also makes sense.

--
With Regards,
Amit Kapila.