Re: Improve list manipulation in several places

Richard Guo <guofenglinux(at)gmail(dot)com> 于2023年4月21日周五 15:35写道：

> There was discussion in [1] about improvements to list manipulation in
> several places. But since the discussion is not related to the topic in
> that thread, fork a new thread here and attach a patch to show my
> thoughts.
>
> Some are just cosmetic changes by using macros. The others should have
> performance gain from the avoidance of moving list entries. But I doubt
> the performance gain can be noticed or measured, as currently there are
> only a few places affected by the change. I still think the changes are
> worthwhile though, because it is very likely that future usage of the
> same scenario can benefit from these changes.
>

I doubt the performance gain from lappend_copy func. new_tail_cell in
lappend may not enter enlarge_list in most cases, because we
may allocate extra cells in new_list(see the comment in new_list).

>
> (Copying in David and Ranier. Ranier provided a patch about the changes
> in list.c, but I'm not using that one.)
>
> [1]
> https://www.postgresql.org/message-id/CAMbWs49aakL%3DPP7NcTajCtDyaVUE-NMVMGpaLEKreYbQknkQWA%40mail.gmail.com
>
> Thanks
> Richard
>