Hi happy year, please remove my contact from the list, thank you very much.


Ing. Jonathan Ruiz

________________________________
De: Stefano <stefanocire...@gmail.com>
Enviado: viernes, 15 de diciembre de 2017 19:56
Para: pgsql-gene...@postgresql.org
Asunto: Re: Replication questions - read-only and temporary read/write slaves

For n.2, you can promote the standby to became a standalone (r/w) server. This 
may be done via "pg_ctl -D $PGDATA promote" or, if in the recovery.conf a 
"triggerfile" definition has been set, touch-ing the triggerfile.
see https://www.postgresql.org/docs/current/static/standby-settings.html
https://www.postgresql.org/docs/10/static/app-pg-ctl.html

regards

2017-12-15 19:30 GMT+01:00 Tiffany Thang 
<tiffanyth...@gmail.com<mailto:tiffanyth...@gmail.com>>:
Thanks Magnus. I did not realize I could use the Hot Standby in read-only mode.

For #2, would it be possible to open the Hot Standby in read/write after 
breaking the replication and taking a snapshot or can Hot Standby only be open 
in read/write after a failover? I hoping I can use the same Hot Standby for 
both #1 and #2.

Thanks again.


On Fri, Dec 15, 2017 at 12:55 PM, Magnus Hagander 
<mag...@hagander.net<mailto:mag...@hagander.net>> wrote:
On Fri, Dec 15, 2017 at 6:03 PM, Tiffany Thang 
<tiffanyth...@gmail.com<mailto:tiffanyth...@gmail.com>> wrote:
Hi,
In PostgreSQL, would it be possible to

1. set up a read-only slave database? The closest solution I could find is Hot 
Standby but the slave would not be accessible until after a failover.

Hot Standby will give you a standby database that is accessible, but in 
read-only mode. This sounds like what you're looking for.


2. temporary convert a read-only slave in read-write mode for testing 
read/write workloads? Currently in Oracle, we can temporary open our read-only 
standby database in read-write mode to occasionally test our read-write 
workloads. We would stop the log apply on the standby database, convert the 
read-only database to read-write,
perform our read/write test, discard all the changes after testing and reopen 
and resync the standby database in read-only mode. Is there a similar feature 
in PostgreSQL or are there ways to achieve something close to our needs?

No, you can't do this with postgres natively.

You could snapshot your filesystem before opening it and then roll back to that 
snapshot, or something like that, but you cannot do it with just PostgreSQL 
functionality.

--
 Magnus Hagander
 Me: https://www.hagander.net/<http://www.hagander.net/>
 Work: https://www.redpill-linpro.com/<http://www.redpill-linpro.com/>




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