From: Tom Lane <tgl@sss.pgh.pa.us>
To: Francisco Olarte <folarte@peoplecall.com>
cc: "David G. Johnston" <david.g.johnston@gmail.com>,
        Wong Simon <thbytwo@live.cn>,
        "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17454: Using psql without ipv4 address,the inet_server_port
 do not return PORT.
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Comments: In-reply-to Francisco Olarte <folarte@peoplecall.com>
	message dated "Sun, 03 Apr 2022 18:28:46 +0200"
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Date: Sun, 03 Apr 2022 12:42:34 -0400
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Francisco Olarte <folarte@peoplecall.com> writes:
>> On Sun, 3 Apr 2022 at 16:50, Wong Simon <thbytwo@live.cn> wrote:
>>> If I run multiple instances on one server with local socket, how can I=
 distinguish them?I think the port is need.

> Port is single valued, what I meant is I'm not sure if using
> socket_dir=3D/socka, listen_addr=3D127.0.0.1, data_dir=3D/dataA and
> port=3D5432 plus socket_dir=3D/sockb, listen_addr=3D127.0.0.2,
> data_dir=3D/datab and port=3D5432 would let you start two correctly
> functioning instances in the same machine.

I think relying on port for this purpose is misguided anyway.
We've had requests in the past to let one postmaster listen on
multiple different port numbers; I think the only reason it's
not happened yet is nobody got excited enough to write a patch.

Likewise, inet_server_addr() seems a bit shaky as a server
identity value, since it's already possible to have a postmaster
listening on multiple IP addresses.

If you're trying to identify an installation uniquely, the
machine name and data_directory are probably the best key.
Getting a suitably unique machine name might be tricky.
For localhost connections, though, you could ignore that.

			regards, tom lane