Standby behavior with setting synchronous_commit = remote_apply

Hi there,

From documentation
https://www.postgresql.org/docs/10/runtime-config-wal.html standby behavior
with setting synchronous_commit = remote_apply is not obvious. I think we
should explain this case.

Am I correct that master always sync COMMIT, except 'off' and regardless of
whether standby is connected or not?

But I am not sure, when standby will sync replayed COMMIT? Does it depend
on synchronous_commit value in standby config?

For example, if synchronous_commit in standbys config is “on”, master
synchronous_standby_names is non-empty, are the following details correct?

synchronous_commit = on

master sync

standby sync

synchronous_commit = remote_apply

master sync

standby ???

synchronous_commit = remote_write

master sync

standby no sync

synchronous_commit = local

master sync

standby no recv

synchronous_commit = off

master sync

standby no recv

--

Konstantin Evteev