Re: Review of Boost.MySql

From: Ruben Perez (rubenperez038_at_[hidden])
Date: 2022-05-15 16:30:36

On Thu, 12 May 2022 at 17:37, Dominique Devienne via Boost
<boost_at_[hidden]> wrote:
>
> On Thu, May 12, 2022 at 4:25 PM Phil Endecott via Boost
> <boost_at_[hidden]> wrote:
> > Ruben Perez wrote (in the doc):
> > >    Warning
> > >    Because of how the MySQL protocol works, once you obtain a resultset,
> > >   you must read it entirely (i.e. until it's complete) before engaging
> > >   in any subsequent operation that implies communication with the server
> > >  (e.g. issuing another query, preparing a statement, closing a
> > >   statement...). Failing to do so results in undefined behavior.
>
> > You are explicitly blaming the protocol for this restriction in
> > that quote. It seems that that is not true, and that it is a
> > limitation of the library.
>
> That's not quite how I interpret it. The (basic) MySQL protocol does indeed
> require the client to fully consume a resultset, and not interleave any other
> operations until that's done, from what Ruben described.
>
> The alternate sequence-diagram Ruben presents, shows writing the next
> query *before* starting to read the first one. It's once you start reading
> that you can't do anything else. And that mode is essentially like having
> the two queries in the same packet, semicolons-separated, something
> also not supported at this point, but which probably should be.

What I meant with that, is that you will have to consume the entire resultset
before starting to consume the next resultset (or the response to any subsequent
request). You can still write stuff to the server, but your replies
will be queued
until you read that resultset. I do think the docs are misleading, and raised
https://github.com/anarthal/mysql/issues/76 to fix it.

>
> It depends Phil. It really helps on slow, high-latency networks.
> In a demo example, manually adding 50ms latency, Larenz Albe got a 4x
> speedup [1].
> But if you run on the LAN with sub-1ms latencies, and/or fast
> Multi-Gb/sec (Cloud) networks,
> it's less likely to matter that much I suspect.

I have raised https://github.com/anarthal/mysql/issues/76 to address pipeline
mode.

Regards,
Ruben.