Re: [HACKERS] [PATCH v1] Add and report the new "in_hot_standby" GUC pseudo-variable. - Mailing list pgsql-hackers

On Wednesday, March 22, 2017 4:28:18 PM EDT Robert Haas wrote:
> On Wed, Mar 22, 2017 at 4:00 PM, Peter Eisentraut 
> > I think we could use "in_recovery", which would be consistent with
> > existing naming.
> 
> True.

Ironically, that was the name I originally used.  I'll update the patch.
> (Jaime's question is also on point, I think.)

The main (and only) point of this patch is to avoid polling.  Since 
"in_recovery" is marked as GUC_REPORT, it will be sent to the client 
asynchronously in a ParamStatus message.  Other GUC_REPORT variables set 
a good precedent.

My argument is that Hot Standby is a major mode of operation, which 
significantly alters how connected clients work with the server, and 
this bit of knowledge is no less important than the other GUC_REPORT 
vars.
                             Elvis