Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>, pgsql-hackers@lists.postgresql.org
Date: 2018-10-02T20:13:28Z
Lists: pgsql-hackers 
Hi,

On 2018-09-26 21:30:25 -0400, Tom Lane wrote:
> Here's a rebased version of <15785.1536776055@sss.pgh.pa.us>.
> 
> I think we should try to get this reviewed and committed before
> we worry more about the float business.  It would be silly to
> not be benchmarking any bigger changes against the low-hanging
> fruit here.

I've looked through the patch. Looks good to me. Some minor notes:

- How about adding our own strchrnul for the case where we don't
  HAVE_STRCHRNUL?  It's possible that other platforms have something
  similar, and the code wouldlook more readable that way.
- I know it's not new, but is it actually correct to use va_arg(args, int64)
  for ATYPE_LONGLONG?

Greetings,

Andres Freund

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().