Re: Enhance pg_stat_wal_receiver view to display connected host

On Fri, Jan 05, 2018 at 09:15:36AM -0300, Alvaro Herrera wrote:
> Haribabu Kommi wrote:
> 
> > And also not returning "default host" details, because for the conninfo
> > without any host details, the return value must be NULL. But this change
> > may break the backward compatibility of the function.
> 
> I wouldn't want to have to fight that battle.

Hm. Any users of psql's PROMPT would be equally confused, and this can
actually lead to more confusion from the user prospective I think than
just pg_stat_wal_receiver. If you take the case of Haribabu from
upthread with say this bit in psqlrc:
\set PROMPT1 '[host=%M;port=%>]=%# '

Then you get on HEAD the following set of results using different
connection strings:
1) host=localhost,localhost hostaddr=127.0.0.1,127.0.0.1 port=5432,5433
[host=localhost,localhost;port=5432]=#

2) host=localhost,localhost port=5432,5433
[host=localhost;port=5432]=# 

3) hostaddr=127.0.0.1,127.0.0.1 port=5432,5433
[host=[local];port=5432]=# 

4) host=/tmp,tmp hostaddr=127.0.0.1,127.0.0.1
[host=[local:/tmp,tmp];port=5432]=# 

So for cases 2) and 4), mixing both hostaddr and host is hurting the
experience. The documentation in [1] also specifies that if both host
and hostaddrs are specified then host is ignored. The same rule applies
for multiple values so for 2) and 4) the correct values ought to be
"local" for both of them. This would be more consistent with the pre-9.6
behavior as well.

[1]: https://www.postgresql.org/docs/current/static/libpq-connect.html
--
Michael