Re: pg_rewind in contrib

26 марта 2015 г., в 7:32, Michael Paquier <michael.paquier@gmail.com> написал(а):

On Thu, Mar 26, 2015 at 12:23 PM, Venkata Balaji N <nag1010@gmail.com> wrote:

Test 1 :

[...]

If the master is crashed or killed abruptly, it may not be possible to do a
rewind. Is my understanding correct ?

Yep. This is mentioned in the documentation:
http://www.postgresql.org/docs/devel/static/app-pgrewind.html
"The target server must shut down cleanly before running pg_rewind».

Test 2 :

- On a successfully running streaming replication with one master and one
slave, i did a clean shutdown of master
- promoted slave
- performed some operations (data changes) on newly promoted slave and did a
clean shutdown
- Executed pg_rewind on the old master to sync with the latest changes on
new master. I got the below message

The servers diverged at WAL position 0/A2000098 on timeline 1.
No rewind required.

I am not getting this too.

In this case the master WAL visibly did not diverge from the slave WAL
line. A rewind is done if the master touches new relation pages after
the standby has been promoted, and before the master is shutdown.
--
Michael


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