| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: The case for removing replacement selection sort |
| Date: | 2017-09-11 15:32:08 |
| Message-ID: | CA+TgmoaoreoVzKx_r08vkSQeDm4MpofANSvsLKKz=FbAXG0j0g@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Sun, Sep 10, 2017 at 9:39 PM, Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> To be clear, you'll still need to set replacement_sort_tuples high
> when testing RS, to make sure that we really use it for at least the
> first run when we're expected to. (There is no easy way to have
> testing mechanically verify that we really do only have one run in the
> end with RS, but I assume that such paranoia is unneeded.)
I seem to recall that raising replacement_sort_tuples makes
replacement selection look worse in some cases -- the optimization is
more likely to apply, sure, but the heap is also bigger, which hurts.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tomas Vondra | 2017-09-11 15:37:45 | Re: Automatic testing of patches in commit fest |
| Previous Message | Tomas Vondra | 2017-09-11 15:17:09 | Re: The case for removing replacement selection sort |