Re: Improve list manipulation in several places

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От Ranier Vilela
Тема Re: Improve list manipulation in several places
Дата
Msg-id CAEudQAokF+4g3f1yGF=FMsG+X52uP72po7SjU8YmUOLnf2R+nA@mail.gmail.com
обсуждение исходный текст
Ответ на Re: Improve list manipulation in several places  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Ответы Re: Improve list manipulation in several places  (Richard Guo <guofenglinux@gmail.com>)
Re: Improve list manipulation in several places  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Список pgsql-hackers
Em seg., 8 de mai. de 2023 às 14:26, Alvaro Herrera <alvherre@alvh.no-ip.org> escreveu:
On 2023-May-08, Peter Eisentraut wrote:

> On 23.04.23 08:42, Richard Guo wrote:
> > Thanks for the suggestion.  I've split the patch into two as attached.
> > 0001 is just a minor simplification by replacing lfirst(list_head(list))
> > with linitial(list).  0002 introduces new functions to reduce the
> > movement of list elements in several places so as to gain performance
> > improvement and benefit future callers.
>
> These look sensible to me.  If you could show some numbers that support the
> claim that there is a performance advantage, it would be even more
> convincing.

0001 looks fine.

The problem I see is that each of these new functions has a single
caller, and the only one that looks like it could have a performance
advantage is list_copy_move_nth_to_head() (which is the weirdest of the
lot).  I'm inclined not to have any of these single-use functions unless
a performance case can be made for them.
I think you missed list_nth_xid, It makes perfect sense to exist.

regards,
Ranier Vilela

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