hot_standby_delta with log shipping

[Krysztophe]

On a replica with log shipping only, the ''hot_standby_delta'' service gives strange results:

receive delta service:nagios_defo13_2 | 656.00 MiB | 100.00 MiB | 1024.00 MiB
replay delta service:nagios_defo13_2 | 0.00 B | 200.00 MiB | 2.00 GiB

In fact , for log shipping, pg_last_wal_receive_lsn is stuck at the end of the recovery.

#  SELECT pg_last_wal_receive_lsn(),  pg_last_wal_replay_lsn() ;
 pg_last_wal_receive_lsn | pg_last_wal_replay_lsn 
-------------------------+------------------------
 1C/EB0001C0             | 1D/11000000

It seems that replacing ''coalesce''' by ''greatest'' in the query works (see

check_pgactivity/check_pgactivity

Line 4227 in 8009e0e

WHEN 't' THEN coalesce(

)

Option: get rid of the "receive" perfdata when pg_last_wal_receive_lsn < pg_last_wal_replay_lsn

[Krysztophe]

BTW this cas occurs only after a switch from streaming to log shipping without restarting the replica.