Re: Logical replication - initial data synchronization

On Sun, Dec 15, 2024 at 11:10 PM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:

> On Mon, Nov 25, 2024 at 11:55 AM Peter Smith <smithpb2250(at)gmail(dot)com>
> wrote:
>
> > "When logical replication of a table starts, PostgreSQL typically
> > takes a snapshot of the table's data on the publisher database and
> > copies it to the subscriber."
> >
> > This makes it clear that "typically" refers to the snapshot-taking
> > process, not the timing of replication's start.
> > ------
> >
> > ======
> > [1]
> https://github.com/postgres/postgres/commit/4c4aaa19a6fed39e0eb0247625331c3df34d8211
> >
>
> Hi Bruce, There was no reply yet to my 3-week-old post above regarding
> (what I thought was) the misplaced word "typically" so I am bumping
> this thread, just in case that post was accidentally overlooked. OTOH,
> if you disagree and/or don't plan to modify it, please let me know so
> I can take this thread off my watch list.
>
>
Not Bruce here.

I concur with this specific wording observation but feel it points to a
larger problem (typically typically does this...).

The whole paragraph seems to boil down to, and would better worded as:

"By default PostgreSQL initiates "transactional replication", whereby when
logical replication begins on each published table PostgreSQL takes a
snapshot and copies those now-static contents to the subscriber.
blah-blah-blah..."

Which begs the question, what about non-transactional replication?

I think we are using "typically" where "default" should be used and then
failing to describe the non-default/non-typical behaviors that also
apparently exist.

I believe this basically boils down to "copy data? true or false" but
haven't tried to reason out enough to be confident in a rewrite that gets
rid of the "typically" with the more definite "default" and mentions the
alternative(s).

I do get we are on the overview page but if we use either typically or
default we still need to lead the reader to the alternatives/knobs even if
it's just a link deeper into the Chapter.

I also get that not everyone uses the term "transactional replication" but
it's our documentation and we should not be afraid to give the process a
label. If we want to mention aliases as an aside that can be considered as
needed.

David J.