Re: why pg_walfile_name() cannot be executed during recovery?

On Fri, Apr 2, 2021 at 4:23 AM SATYANARAYANA NARLAPURAM
<satyanarlapuram(at)gmail(dot)com> wrote:
> Why pg_walfile_name() can't be executed under recovery?

I believe the issue is that the backend executing the function might
not have an accurate idea about which TLI to use. But I don't
understand why we can't find some solution to that problem.

> What is the best way for me to get the current timeline and/or the file being recovering on the standby using a postgres query? I know I can get it via process title but don't want to go that route.

pg_stat_wal_receiver has LSN and TLI information, but probably won't
help except when WAL receiver is actually active.
pg_last_wal_receive_lsn() and pg_last_wal_replay_lsn() will give the
LSN at any point during recovery, but not the TLI. We might have some
gaps in this area...

--
Robert Haas
EDB: http://www.enterprisedb.com