Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Paquier <michael.paquier@gmail.com>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Date: 2017-09-29T22:54:58Z
Lists: pgsql-hackers

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On 2017-09-29 17:56:10 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > Does anybody have an opinion on whether we'll want to convert examples
> > like testlibpq3.c (included in libpq.sgml) too? I'm inclined not to,
> > because currently using pg_bswap.h requires c.h presence (just for a few
> > typedefs and configure data).  There's also not really a pressing need.
>
> We certainly mustn't encourage libpq users to start depending on c.h,
> so let's leave that alone.

Here's two patches:

0001: Previously submitted changes to pg_bswap.h, addressing concerns
      like the renaming
0002: Move over most users of ntoh[sl]/hton[sl] over to pg_bswap.h.

Note that the latter patch includes replacing open-coded byte swapping
of 64bit integers (using two 32 bit swaps) with a single 64bit
swap. I've also removed pg_recvint64 - it's now a single pg_ntoh64 - as
it's name strikes me as misleading.

Where it looked applicable I have removed netinet/in.h and arpa/inet.h
usage, which previously provided the relevant functionality. It's
perfectly possible that I missed other reasons for including those,
the buildfarm will tell.

Greetings,

Andres Freund

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.