Re: computing completion tag is expensive for pgbench -S -M prepared - Mailing list pgsql-hackers

On 2018-06-07 10:30:14 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > ...  That's actually fairly trivial to optimize - we don't
> > need the full blown snprintf machinery here.  A quick benchmark
> > replacing it with:
> 
> >                        memcpy(completionTag, "SELECT ", sizeof("SELECT "));
> >                        pg_lltoa(nprocessed, completionTag + 7);
> 
> While I don't have any objection to this change if the speedup is
> reproducible, I do object to spelling the same constant as
> 'sizeof("SELECT ")' and '7' on adjacent lines ...

Hah, yes. Nor would I want to keep the #if 0 around it ;).  I mostly
wanted to know whether others can reproduce the effect - the actual
patch would need to be bigger and affect more places.

Greetings,

Andres Freund