Re: PATCH: Batch/pipelining support for libpq

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Daniel Verite <daniel(at)manitou-mail(dot)org>
Cc: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Matthieu Garrigues <matthieu(dot)garrigues(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Dave Cramer <davecramer(at)postgres(dot)rocks>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Vaishnavi Prabakaran <vaishnaviprabakaran(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)iki(dot)fi>
Subject: Re: PATCH: Batch/pipelining support for libpq
Date: 2020-11-18 17:51:34
Message-ID: 20201118175134.GA30739@alvherre.pgsql
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On 2020-Nov-14, Daniel Verite wrote:

> The patch I posted in [1] was pretty simple, but at the time, query
> results were always discarded. Now that pgbench can instantiate
> variables from query results, a script can do:
> select 1 as var \gset
> select :var;
> This kind of sequence wouldn't work in batch mode since it
> sends queries before getting results of previous queries.
> So maybe \gset should be rejected when inside a batch section.


Hacking pgbench extensively is beyond what I'm willing to do for this
feature at this time. Making \gset rejected in a batch section sounds
simple enough and supports \beginbatch et al sufficiently to compare
performance, so I'm OK with a patch that does that. That'd be a small
extension to your previous patch, if I understand correctly.

If you or others want to send patches to extend batch support with
read-write tracking for variables, feel free, but I hereby declare that
I'm not taking immediate responsibility for getting them committed.

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