Обсуждение: How to downgrade a cluster from 9.5 to 9.3

Hello all. My first post. 

I have a ubuntu machine that was originally running postgres 9.3. I
installed 9.5 on that machine as well and then performed a pg_upgradecluster
-v 9.5. 9.3 main.
This procedure successfully moved my data from the running 9.3/main cluster,
to the 9.5/main cluster, brought down the 9.3 running instance and then
brought the 9.5 instance online utilizing the default ports. This was neat
to see happen.  

As a back out plan, I need to know how to restore the 9.3 running instance
if for some reason the data got corrupted in the update to 9.5. 

Does anyone have experience doing this and if so, how did you accomplish?

Thank you in advance.



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On 10/11/2018 16:25, Michael Lupo wrote:
> Hello all. My first post. 
> 
> I have a ubuntu machine that was originally running postgres 9.3. I
> installed 9.5 on that machine as well and then performed a pg_upgradecluster
> -v 9.5. 9.3 main.
> This procedure successfully moved my data from the running 9.3/main cluster,
> to the 9.5/main cluster, brought down the 9.3 running instance and then
> brought the 9.5 instance online utilizing the default ports. This was neat
> to see happen.  
> 
> As a back out plan, I need to know how to restore the 9.3 running instance
> if for some reason the data got corrupted in the update to 9.5.

You should be able to just shut down the 9.5 instance, switch back the
port numbers, and start the 9.3 instance.

Note that pg_upgradecluster by default uses the pg_dump method, so it's
unlikely that anything will get "corrupted" during the upgrade.  It's a
more interesting consideration if you use the pg_upgrade method.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services