From: Tom Lane <tgl@sss.pgh.pa.us>
To: Fabien COELHO <coelho@cri.ensmp.fr>
cc: Corey Huinker <corey.huinker@gmail.com>,
        Daniel Verite <daniel@manitou-mail.org>,
        "David G. Johnston" <david.g.johnston@gmail.com>,
        Greg Stark <stark@mit.edu>, Erik Rijkers <er@xs4all.nl>,
        Robert Haas <robertmhaas@gmail.com>,
        Jim Nasby <Jim.Nasby@bluetreble.com>,
        PostgreSQL <pgsql-hackers@postgresql.org>,
        pgsql-hackers-owner@postgresql.org
Subject: Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if,
 \quit_unless)
In-reply-to: <alpine.DEB.2.20.1703171553550.21944@lancre>
References: <df2c433c-b9ff-4d41-ad08-b0d420b403b8@manitou-mail.org>
 <15875.1489440118@sss.pgh.pa.us>
 <CADkLM=fzjNr2it+a75CJgs7nPPSb-S=q=taa7=7mtxa5pKJSbQ@mail.gmail.com>
 <24741.1489698878@sss.pgh.pa.us>
 <CADkLM=fHrBW4Z+ixPD35Ad+4oKG1KX0UK7xDY+0G9gdNnDQS8A@mail.gmail.com>
 <alpine.DEB.2.20.1703170710320.4278@lancre> <30537.1489761433@sss.pgh.pa.us>
 <alpine.DEB.2.20.1703171553550.21944@lancre>
Comments: In-reply-to Fabien COELHO <coelho@cri.ensmp.fr>
	message dated "Fri, 17 Mar 2017 16:32:33 +0100"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <11742.1489765330.1@sss.pgh.pa.us>
Date: Fri, 17 Mar 2017 11:42:10 -0400
Message-ID: <11743.1489765330@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Fabien COELHO <coelho@cri.ensmp.fr> writes:
>> I also fear that there are corner cases where the behavior would still
>> be inconsistent.  Consider
>> 
>> \if ...
>> \set foo `echo \endif should not appear here`

> In this instance, ISTM that there is no problem. On "\if true", set is 
> executed, all is well. On "\if false", the whole line would be skipped 
> because the if-related commands are only expected on their own line, all 
> is well again. No problem.

AFAICS, you misunderstood the example completely, or else you're proposing
syntax restrictions that are even more bizarre and unintelligible than
I thought before.  We cannot have a situation where the syntax rules for
backslash commands inside an \if are fundamentally different from what
they are elsewhere; that's just going to lead to confusion and bug
reports.

			regards, tom lane


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers