| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | 孙冰 <subi(dot)the(dot)dream(dot)walker(at)gmail(dot)com> |
| Cc: | "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: The hidden cost of limit-offset |
| Date: | 2020-12-06 16:05:41 |
| Message-ID: | CAKFQuwbAa0Qgxiy3h55AjnysixgLFZwriQw-MrFC0QTSG9ysAg@mail.gmail.com |
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| Lists: | pgsql-general |
On Sunday, December 6, 2020, 孙冰 <subi(dot)the(dot)dream(dot)walker(at)gmail(dot)com> wrote:
> The skipped rows by an OFFSET clause have to be computed nevertheless. I
> am wondering if there could be any chance to improve, since the computation
> is on the *entire* rows rather than on the *criterial* columns.
>
> [...]
>
> I don't understand the postgresql internal, but I suspect such a change
> may introduce significant work on the planner and executor. From my point
> view, skipping everything (or expensive ones) except the criteria in the
> target list would greatly improve the usability of OFFSET, and it is
> definitely worth the effort.
>
Given that one can write this with a subquery without much difficulty i’m
doubtful that effort spent in this area is going to be particularly
valuable.
David J.
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