Horton

Re: Performance improvements for src/port/snprintf.c

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org, Thomas Munro <thomas.munro@enterprisedb.com>, Andrew Gierth <andrew@tao11.riddles.org.uk>, Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>
Date: 2018-10-03T17:40:03Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2018-10-03 13:31:09 -0400, Tom Lane wrote:
>> I do not see the point of messing with snprintf.c here.  I doubt that
>> strfromd is faster than the existing sprintf call (because the latter
>> can use ".*" instead of serializing and deserializing the precision).

> I'm confused, the numbers I posted clearly show that it's faster?

Those were in the context of whether float8out went through snprintf.c
or directly to strfromd, no?

			regards, tom lane

Commits

  1. Improve snprintf.c's handling of NaN, Infinity, and minus zero.

  2. Rationalize snprintf.c's handling of "ll" formats.

  3. Provide fast path in snprintf.c for conversion specs that are just "%s".

  4. Make assorted performance improvements in snprintf.c.

  5. Set snprintf.c's maximum number of NL arguments to be 31.

  6. Always use our own versions of *printf().