Re: [PATCH] Incremental sort (was: PoC: Partial sort)
От | Tomas Vondra |
---|---|
Тема | Re: [PATCH] Incremental sort (was: PoC: Partial sort) |
Дата | |
Msg-id | 20200405131227.zit6a5w3fv5qq6fh@development обсуждение исходный текст |
Ответ на | Re: [PATCH] Incremental sort (was: PoC: Partial sort) (Tomas Vondra <tomas.vondra@2ndquadrant.com>) |
Список | pgsql-hackers |
On Sun, Apr 05, 2020 at 03:01:10PM +0200, Tomas Vondra wrote: >On Thu, Apr 02, 2020 at 09:40:45PM -0400, James Coleman wrote: >>On Thu, Apr 2, 2020 at 8:46 PM James Coleman <jtc331@gmail.com> wrote: >>> >>>On Thu, Apr 2, 2020 at 8:20 PM Tomas Vondra >>><tomas.vondra@2ndquadrant.com> wrote: >>>> ... >>>> 5) Overall, I think the costing is OK. I'm sure we'll find cases that >>>> will need improvements, but that's fine. However, we now have >>>> >>>> - cost_tuplesort (used to be cost_sort) >>>> - cost_full_sort >>>> - cost_incremental_sort >>>> - cost_sort >>>> >>>> I find it a bit confusing that we have cost_sort and cost_full_sort. Why >>>> don't we just keep using the dummy path in label_sort_with_costsize? >>>> That seems to be the only external caller outside costsize.c. Then we >>>> could either make cost_full_sort static or get rid of it entirely. >>> >>>This another area of the patch I haven't really modified. >> >>See attached for a cleanup of this; it removed cost_fullsort so >>label_sort_with_costsize is back to how it was. >> >>I've directly merged this into the patch series; if you'd like to see >>the diff I can send that along. >> > >Thanks. Attached is v54 of the patch, with some minor changes. The main >two changes are in add_partial_path_precheck(), firstly to also consider >startup_cost, as discussed before. The second change (in 0003) is a bit >of an experiment to make add_partial_precheck() cheaper by only calling >compare_pathkeys after checking the costs first (which should be cheaper >than the function call). add_path_precheck already does it in that order >anyway. > Oh, I forgot to mention a change in add_partial_path - I've removed the reference/dependency on enable_incrementalsort. It seemed rather ugly, and the results without it seem fine (I'm benchmarking only the case with incremental sort enabled anyway). I also plan to look at the other optimization we bolted on last week, i.e. checking length of pathkeys. I'll see if that actually makes measurable difference. regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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