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From: Subramanian,Ramachandran <ramachandran.subramanian@alte-leipziger.de>
To: Laurenz Albe <laurenz.albe@cybertec.at>
To: pgsql-novice@lists.postgresql.org <pgsql-novice@lists.postgresql.org>
Subject: AW: AW: Replication Testing- How to introduce a Lag
Date: Sat, 21 Mar 2026 07:49:32 +0000
Message-ID: <fa47fe18078043adbdfe007b7270ffd0@alte-leipziger.de> (raw)
In-Reply-To: <8b38fa5141905f9ad6983b8d5ae944e812e3d28a.camel@cybertec.at>
References: <aadb9058660d4e10b5cee44b82458802@alte-leipziger.de>
	<f3927bc3a9baf4400325b91652869907f0581c97.camel@cybertec.at>
	<e1e41761323040228570cf6a7e02518e@alte-leipziger.de>
	<8b38fa5141905f9ad6983b8d5ae944e812e3d28a.camel@cybertec.at>

> how can the last replayed be more than the last received?

It shouldn't be - but I don't understand your script, in particular which query is issused on which server.

[Subramanian,Ramachandran IT-md-db] 
100% sure that I have screwed up some variables in my script

Look at "pg_stat_replication" on the primary server.

[Subramanian,Ramachandran IT-md-db] 

Thank you so much!!  So I do not have to go across multiple tables to collect the information. 

It is all there in one table pg_stat_replication at the Primary server and we can look at it from A) Primary and also from B) Stand-by !! 

If I just look at the write_lag columns, it would give me a good idea of the situation --  Is my understanding correct ?

LG

Ram


Details from the Source (Remote Primary)
----------------------------------------------------------

pid   | usesysid |  usename   | application_name | client_addr | client_hostname | client_port |         backend_start
  | backend_xmin |   state   |  sent_lsn  | write_lsn  | flush_lsn  | replay_lsn |    write_lag    |    flush_lag    |   replay
_lag    | sync_priority | sync_state |          reply_time
--------+----------+------------+------------------+-------------+-----------------+-------------+-----------------------------
--+--------------+-----------+------------+------------+------------+------------+-----------------+-----------------+---------
--------+---------------+------------+-------------------------------
 188833 |    25200 | replicator | walreceiver      | 10.10.10.10  |                 |       43330 | 2026-03-21 08:11:37.010895+0
1 |              | streaming | 0/49072590 | 0/49072590 | 0/49072590 | 0/49042F98 | 00:00:00.000463 | 00:00:00.001693 | 00:00:27
.042262 |             0 | async      | 2026-03-21 08:12:19.239535+01
(1 row)

The same details from the Local Stand-by Server -- They match !!!!
----------------------------------------------------------------------------------

pg_last_wal_receive_lsn
-------------------------
 0/49072590
(1 row)

 pg_last_wal_replay_lsn
------------------------
 0/49042F98
(1 row)


Freundliche Grüße

i. A. Ramachandran Subramanian
Zentralbereich Informationstechnologie

Alte Leipziger Lebensversicherung a.G.


Hallesche Krankenversicherung a.G.





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