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Thread: pgsql: Use quicksort, not replacement selection, for external sorting.

pgsql: Use quicksort, not replacement selection, for external sorting.

From
Robert Haas
Date:
Use quicksort, not replacement selection, for external sorting.

We still use replacement selection for the first run of the sort only
and only when the number of tuples is relatively small.  Otherwise,
the first run, and subsequent runs in all cases, are produced using
quicksort.  This tends to be faster except perhaps for very small
amounts of working memory.

Peter Geoghegan, reviewed by Tomas Vondra, Jeff Janes, Mithun Cy,
Greg Stark, and me.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/0711803775a37e0bf39d7efdd1e34d9d7e640ea1

Modified Files
--------------
doc/src/sgml/config.sgml                      |  39 +++
src/backend/optimizer/path/costsize.c         |   6 +-
src/backend/utils/init/globals.c              |   1 +
src/backend/utils/misc/guc.c                  |  10 +
src/backend/utils/misc/postgresql.conf.sample |   1 +
src/backend/utils/sort/tuplesort.c            | 463 +++++++++++++++++++++-----
src/include/miscadmin.h                       |   1 +
7 files changed, 430 insertions(+), 91 deletions(-)

Re: pgsql: Use quicksort, not replacement selection, for external sorting.

From
Tom Lane
Date:
Robert Haas <rhaas@postgresql.org> writes:
> Use quicksort, not replacement selection, for external sorting.

This patch evidently broke several of the Windows buildfarm critters,
eg on mastodon:

Build FAILED.
.\src\backend\utils\sort\tuplesort.c(2373): error C2143: syntax error : missing ';' before 'type'
.\src\backend\utils\sort\tuplesort.c(2377): error C2065: 'ntuples' : undeclared identifier
    0 Warning(s)
    2 Error(s)



            regards, tom lane

Re: pgsql: Use quicksort, not replacement selection, for external sorting.

From
Tom Lane
Date:
I wrote:
> Robert Haas <rhaas@postgresql.org> writes:
>> Use quicksort, not replacement selection, for external sorting.

> This patch evidently broke several of the Windows buildfarm critters,

On inspection, the problem is obviously "declaration in the middle of
a code block".

            regards, tom lane

Re: pgsql: Use quicksort, not replacement selection, for external sorting.

From
Robert Haas
Date:
On Fri, Apr 8, 2016 at 10:47 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I wrote:
>> Robert Haas <rhaas@postgresql.org> writes:
>>> Use quicksort, not replacement selection, for external sorting.
>
>> This patch evidently broke several of the Windows buildfarm critters,
>
> On inspection, the problem is obviously "declaration in the middle of
> a code block".

Woops.  Attempted a fix.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company