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

On 13 April 2017 at 14:59, Tsunakawa, Takayuki
<tsunakawa.takay@jp.fujitsu.com> wrote:

> 2. Make transaction_read_only GUC_REPORT
> This is to avoid the added round-trip by SHOW command.  It also benefits client apps that want to know when the
servergets promoted?  And this may simplify the libpq code. 
> I don't understand yet why we need to provide this feature for older servers by using SHOW.  Those who are already
using<= 9.6 in production completed the system or application, and their business is running.  Why would they want to
justreplace libpq and use this feature? 

I think "transaction_read_only" is a bit confusing for something we're
expecting to change under us.

To me, a "read only" xact is one created with

BEGIN READ ONLY TRANSACTION;

.... which I would not expect to become read/write under me, since I
explicitly asked for read-only.

It's more like "session read only" that we're interested in IMO.