Horton

Re: SendRowDescriptionMessage() is slow for queries with a lot of columns

Alvaro Herrera <alvherre@alvh.no-ip.org>

View thread View on postgr.es
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-10-11T08:53:56Z
Lists: pgsql-hackers 
Andres Freund wrote:
> Hi,
> 
> On 2017-10-03 13:58:37 -0400, Robert Haas wrote:
> > On Tue, Oct 3, 2017 at 12:23 PM, Andres Freund <andres@anarazel.de> wrote:
> > > Makes sense?
> > 
> > Yes.
> 
> Here's an updated version of this patchset.

Maybe it'd be a good idea to push 0001 with some user of restrict ahead
of the rest, just to see how older msvc reacts.

I wonder if it'd be a good idea to nag external users about pq_sendint
usage (is a #warning possible?).  OTOH, do we really need to keep it
around?  Maybe we should ditch it, since obviously the compat shim can
be installed locally in each extension that really needs it (thinking
that most external code can simply be adjusted to the new functions).

I'm scared about the not-null-terminated stringinfo stuff.  Is it
possible to create bugs by polluting a stringinfo with it, then having
the stringinfo be used by unsuspecting code?  Admittedly, you can break
things already with the binary appends, so probably not an issue.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Replace remaining uses of pq_sendint with pq_sendint{8,16,32}.

  2. Improve performance of SendRowDescriptionMessage.

  3. Use one stringbuffer for all rows printed in printtup.c.

  4. Add configure infrastructure to detect support for C99's restrict.

  5. Add more efficient functions to pqformat API.

  6. Allow to avoid NUL-byte management for stringinfos and use in format.c.

  7. Replace most usages of ntoh[ls] and hton[sl] with pg_bswap.h.

  8. Extend & revamp pg_bswap.h infrastructure.