Logical subscription / publication lifetimes

On Fri, Apr 22, 2022 at 5:00 AM andrew cooke <andrew@acooke.org> wrote:

If I define a publication at time Tp, then load some data on the
publisher, then start a subscription at time Ts, then load some more
data on the publisher, does the subscriber get data from Tp or Ts
onwards?

It depends. By default, neither, the publisher is publishing the entire
contents of the table and the subscriber will do everything necessary to
replicate those contents in their entirety.

If you specify copy_data = false I'm not sure what you end up with
initially or after disable. My guess is the subscription defines the first
transaction it cares about when it connects to the publisher, defaulting to
the most recent publisher transaction (all older transactions would be
handled via copy_data = true) but then so long as the slot remains active
the publisher will place the data into the slot even while the subscriber
is not active and the subscriber will receive all of it next time it comes
online/re-enables.

David J.

Ah, thanks! I should have read the documentation of all the
parameters!

So the portion of data that is covered by "copy_data" is going to
reflect updates and deletes prior to the creation of the slot even if
"publish=insert" (only)?

This makes sense because I can't see how else it could be practically
implemented, but just want to be sure I am understanding. The idea
that there are two phases (copy existing data then replicate
operations) is a big help.

Thanks again,
Andrew