Date: Sun, 19 Mar 2017 17:00:07 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>,
	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)
Message-ID: <20170319200007.2qol6aqyzowmodvc@alvherre.pgsql>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <27329.1489945688@sss.pgh.pa.us>
User-Agent: NeoMutt/20170206-195-7adf12 (1.7.2)
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Tom Lane wrote:

> I'm not entirely convinced that function-per-command is an improvement
> though.  Seems like it would only help to the extent that you could do a
> simple "return" to implement early exit, and it looks to me like that
> doesn't work in a lot of places because you still have to clean up things
> like malloc'd argument strings before you can return.  So the question
> we have to answer is whether this way looks cleaner than what we'd get if
> we just changed the logic in-place.  For the purpose of answering that
> question, looking at the final state is the right thing to do.
> 
> I don't have a definite opinion on that core question yet, since I've not
> read this version of the patch.  Anybody else want to give an opinion?

Currently, exec_command is a 1500-line function.  If I had to see how a
single \-command worked, I would have to fold everything but the command
I'm interested in, in case there's something nontrivial at function
start or end (or even in between -- I would have to start by figuring
out whether there's anything other than "else if" somewhere in those
1500 lines).  I think splitting into command-specific functions makes
this much easier to follow, particularly if we want to add extra tricks
such as returning early etc.

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


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