From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Fabien COELHO <coelho@cri.ensmp.fr>,
 Michael Paquier <michael@paquier.xyz>,
        Stephen Frost <sfrost@snowman.net>,
        Andrew Dunstan <andrew.dunstan@2ndquadrant.com>,
        PostgreSQL Developers <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] pgbench - allow to store select results into variables
In-reply-to: <201901101900.mv7zduch6sad@alvherre.pgsql>
References: <201901101900.mv7zduch6sad@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Thu, 10 Jan 2019 16:00:33 -0300"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <4244.1547147665.1@sss.pgh.pa.us>
Date: Thu, 10 Jan 2019 14:14:25 -0500
Message-ID: <4245.1547147665@sss.pgh.pa.us>
Precedence: bulk

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2019-Jan-10, Tom Lane wrote:
>> This \cset thing seem like an incredibly badly thought out kluge.
>> What is its excuse to live?

> The reason is that you can set variables from several queries in one
> network trip.

So who needs that?  Just merge the queries, if it's so important that
you avoid multiple round trips.

> We can take it out I guess, but my impression was that we already pretty
> much had a consensus that it was wanted. 

Maybe if the implementation weren't a pile of junk it'd be all right,
but as-is this is a mess.  The dependency on counting \; in particular
is setting me off, because that has little if anything to do with the
number of query results to be expected.  I imagine the argument will
be that nobody would write the sort of queries that break that assumption
in a pgbench script; but I don't find that kind of design to be up
to project standards, especially not when the argument for the feature
is tissue-thin in the first place.

			regards, tom lane