Hi,
I would like to clarify something about standby promotion. From the sentence below. I understand that, during the promotion process, postgres will replay all the available wals (from the archive or pg_xlog).
https://www.postgresql.org/docs/9.5/static/warm-standby.html#STREAMING-REPLICATION
...
Standby mode is exited and the server switches to normal operation when pg_ctl promote is run or a trigger file is found (trigger_file). Before failover, any WAL immediately available in the archive or in pg_xlog will be restored, but no attempt is made to connect to the master.
I have seen several articles like this one (https://www.enterprisedb.com/switchoverswitchback-postgresql-93) where they say that pg_last_xlog_receive_location() and pg_last_xlog_replay_location() should be checked before promotion. I don't understand why since they will be replayed anyway. Did something changed since 9.3 about this ?
Thanks for you help. please excuse my poor english.
Benoit
