Date: Wed, 21 Aug 2019 10:16:36 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>,
	Dilip Kumar <dilipbalaut@gmail.com>, jungleboogie0@gmail.com,
	pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15964: vacuumdb.c:187:10: error: use of undeclared
 identifier 'FD_SETSIZE'
Message-ID: <20190821141636.GA26948@alvherre.pgsql>
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On 2019-Aug-21, Michael Paquier wrote:

> On Wed, Aug 21, 2019 at 09:49:54AM -0400, Alvaro Herrera wrote:

> > Well, it's a user-facing error, so I'd rather make it user-friendly.
> > It doesn't seem difficult, or unreliable enough not to try.
> 
> Still, in this case, because of the nature of FD_SETSIZE the hint may
> finish by being wrong, no?  I am not sure that it is worth going this
> way.

Theoretically it is possible that we give a wrong hint, but I think it's
hardly a practical reality.  I'd rather give the hint and tell the user
what a reasonable parameter might be.  If they run under a different
environment (I dunno, they use shell invocation line with other
redirections I guess), then they might get a different hint next time.
So what?

I guess the other possibility is that there exists an operating system
that returns file descriptors higher than its FD_SETSIZE, when some fds
below FD_SETSIZE are still available.  Doesn't seem realistic.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services