| From: | Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, rushabh(dot)lathia(at)gmail(dot)com |
| Subject: | Re: [PATCH] Keeps tracking the uniqueness with UniqueKey |
| Date: | 2020-06-05 02:36:39 |
| Message-ID: | CAKU4AWpUSpOS1YCt6zhZsNYpD2NkTUDVv+HLOvewbHnADtAb0g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, May 25, 2020 at 2:34 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> On Sun, 24 May 2020 at 04:14, Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:
> >
> > > On Fri, May 22, 2020 at 08:40:17AM +1200, David Rowley wrote:
> > > I imagine we'll set some required UniqueKeys during
> > > standard_qp_callback()
> >
> > In standard_qp_callback, because pathkeys are computed at this point I
> > guess?
>
> Yes. In particular, we set the pathkeys for DISTINCT clauses there.
>
>
Actually I have some issues to understand from here, then try to read index
skip scan patch to fully understand what is the requirement, but that
doesn't
get it so far[1]. So what is the "UniqueKeys" in "UniqueKeys during
standard_qp_callback()" and what is the "pathkeys" in "pathkeys are computed
at this point” means? I tried to think it as root->distinct_pathkeys,
however I
didn't fully understand where root->distinct_pathkeys is used for as well.
--
Best Regards
Andy Fan
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