Re: PATCH: Batch/pipelining support for libpq

From: 'Alvaro Herrera' <alvherre(at)alvh(dot)no-ip(dot)org>
To: "k(dot)jamison(at)fujitsu(dot)com" <k(dot)jamison(at)fujitsu(dot)com>
Cc: Craig Ringer <craig(dot)ringer(at)enterprisedb(dot)com>, Matthieu Garrigues <matthieu(dot)garrigues(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: PATCH: Batch/pipelining support for libpq
Date: 2021-03-04 01:51:08
Message-ID: 20210304015108.GA15670@alvherre.pgsql
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On 2021-Mar-03, 'Alvaro Herrera' wrote:

> On 2021-Mar-03, 'Alvaro Herrera' wrote:
> > This should obviously not occur. I'm trying to figure out how to repair
> > it and not break everything again ...
> I think trying to set up the connection state so that the next query
> appears in conn->last_query prior to PQgetResult being called again
> leads to worse breakage. The simplest fix seems to make fe-protocol3.c
> aware that in this case, the query is in conn->cmd_queue_head instead,
> as in the attached patch.

I wonder if it would make sense to get rid of conn->last_query
completely and just rely always on conn->cmd_queue_head, where the
normal (non-pipeline) would use the first entry of the command queue.
That might end up being simpler than pipeline mode "pretending" to take
over ->last_query.

Álvaro Herrera 39°49'30"S 73°17'W
"La verdad no siempre es bonita, pero el hambre de ella sí"

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