Hi,
On 6/7/23 7:32 AM, Jaime Casanova wrote:
Hi,
I'm testing the ability to have a logical replica subscribed from a standby.
Of course, I'm doing this in a laboratory with no activity so
everything get stuck after creating the subscription (the main slot).
This is clearly because every time it will create a temp slot for copy
a table it needs the running xacts from the primary.
Now, I was solving this by executing CHECKPOINT on the primary, and
also noted that pg_switch_wal() works too. After that, I read about
pg_log_standby_snapshot().
So, I wonder if that function is really needed because as I said I
solved it with already existing functionality. Or if it is really
needed maybe it is a bug that a CHECKPOINT and pg_switch_wal() have
the same effect?
Even if CHECKPOINT and pg_switch_wal() do produce the same effect, I think
they are expensive (as compare to pg_log_standby_snapshot() which does nothing
but
emit a xl_running_xacts).
For this reason, I think pg_log_standby_snapshot() is worth to have/keep.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
