Date: Thu, 10 Jan 2019 16:49:35 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
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
Message-ID: <201901101949.wdjmpfsh6hzw@alvherre.pgsql>
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On 2019-Jan-10, Tom Lane wrote:

> 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.

Hmm, I suppose that's true.

> > 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.

There's a lot of the new code in pgbench that can be simplified if we
remove \cset.

I'll leave time for others to argue for or against cset, and then act
accordingly.

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