Horton

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

Mithun Cy <mithun.cy@enterprisedb.com>

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From: Mithun Cy <mithun.cy@enterprisedb.com>
To: Andres Freund <andres@anarazel.de>
Cc: Thom Brown <thom@linux.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-09-20T06:18:13Z
Lists: pgsql-hackers 
On Mon, Sep 18, 2017 at 1:38 PM, Mithun Cy <mithun.cy@enterprisedb.com> wrote:
> On Sat, Sep 16, 2017 at 3:03 AM, Andres Freund <andres@anarazel.de> wrote:
> So I think performance gain is visible. We saved a good amount of
> execution cycle in SendRowDescriptionMessagewhen(my callgrind report
> confirmed same) when we project a large number of columns in the query
> with these new patches.

I have tested patch, for me, patch looks good and can see improvement
in performance as a number of columns projected increases in the
query. There appear some cosmetic issues(pgindent issues + end of file
cr) in the patch if it can be considered as a valid issue they need
changes. Rest look okay for me.

-- 
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com

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.