Re: Logical replication - initial data synchronization - Mailing list pgsql-docs

From David G. Johnston
Subject Re: Logical replication - initial data synchronization
Date
Msg-id CAKFQuwa9CXk53OySJNywvWBdve0ZkdU2KTMWK=O5+Y26cuqHNw@mail.gmail.com
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In response to Re: Logical replication - initial data synchronization  (Peter Smith <smithpb2250@gmail.com>)
Responses Re: Logical replication - initial data synchronization
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On Sun, Dec 15, 2024 at 11:10 PM Peter Smith <smithpb2250@gmail.com> wrote:
On Mon, Nov 25, 2024 at 11:55 AM Peter Smith <smithpb2250@gmail.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.

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