| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, David Rowley <dgrowleyml(at)gmail(dot)com>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
| Subject: | Re: Improve list manipulation in several places |
| Date: | 2023-05-09 03:13:44 |
| Message-ID: | CAMbWs4-CzhHggsPeTToMQ4K5MMd4y7vcQsP5Cd2DTaoRuyGX+A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, May 9, 2023 at 1:26 AM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
wrote:
> 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.
Yeah, maybe this is the reason I failed to devise a query that shows any
performance gain. I tried with a query which makes the 'all_pathkeys'
in sort_inner_and_outer being length of 500 and still cannot see any
notable performance improvements gained by list_copy_move_nth_to_head.
Maybe the cost of other parts of planning swamps the performance gain
here? Now I agree that maybe 0002 is not worthwhile to do.
Thanks
Richard
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