Re: Flushing large data immediately in pqcomm

Ranier Vilela <ranier.vf@gmail.com>

From: Ranier Vilela <ranier.vf@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Jelte Fennema-Nio <postgres@jeltef.nl>, David Rowley <dgrowleyml@gmail.com>, Melih Mutlu <m.melihmutlu@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>, Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>
Date: 2024-04-07T12:42:54Z
Lists: pgsql-hackers
Em sáb., 6 de abr. de 2024 às 22:39, Andres Freund <andres@anarazel.de>
escreveu:

> Hi,
>
> On 2024-04-07 00:45:31 +0200, Jelte Fennema-Nio wrote:
> > On Sat, 6 Apr 2024 at 22:21, Andres Freund <andres@anarazel.de> wrote:
> > > The small regression for small results is still kinda visible, I
> haven't yet
> > > tested the patch downthread.
> >
> > Thanks a lot for the faster test script, I'm also impatient. I still
> > saw the small regression with David his patch. Here's a v6 where I
> > think it is now gone. I added inline to internal_put_bytes too. I
> > think that helped especially because for two calls to
> > internal_put_bytes len is a constant (1 and 4) that is smaller than
> > PqSendBufferSize. So for those calls the compiler can now statically
> > eliminate the new codepath because "len >= PqSendBufferSize" is known
> > to be false at compile time.
>
> Nice.
>
>
> > Also I incorporated all of Ranier his comments.
>
> Changing the global vars to size_t seems mildly bogus to me. All it's
> achieving is to use slightly more memory. It also just seems unrelated to
> the
> change.
>
I don't agree with this thought.
Actually size_t uses 4 bytes of memory than int, right.
But mixing up int and size_t is a sure way to write non-portable code.
And the compilers will start showing messages such as " signed/unsigned
mismatch".

The global vars PqSendPointer and PqSendStart were changed in the v5 patch,
so for the sake of style and consistency, I understand that it is better
not to mix the types.

The compiler will promote PqSendBufferSize to size_t in all comparisons.

And finally the correct type to deal with char * variables is size_t.

Best regards,
Ranier Vilela


> Greetings,
>
> Andres Freund
>

Commits

  1. Avoid needless large memcpys in libpq socket writing