| From: | Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com> |
|---|---|
| To: | James Coleman <jtc331(at)gmail(dot)com> |
| Cc: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Floris Van Nee <florisvannee(at)optiver(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Bhushan Uparkar <bhushan(dot)uparkar(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Subject: | Re: Index Skip Scan |
| Date: | 2020-03-11 10:56:09 |
| Message-ID: | CAKU4AWp17_mnb1o8kZoc-cqvfmELs9bpeSXM9kroMgSy4xuRjg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Mar 10, 2020 at 4:32 AM James Coleman <jtc331(at)gmail(dot)com> wrote:
> On Mon, Mar 9, 2020 at 3:56 PM Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
> wrote:
> >
> > Assuming we'll implement it in a way that we do not know about what kind
> > of path type is that in create_distinct_path, then it can also work for
> > ProjectionPath or anything else (if UniqueKeys are present). But then
> > still EquivalenceMember are used only to figure out correct
> > distinctPrefixKeys and do not affect whether or not skipping is applied.
> > What do I miss?
>
>
> Part of the puzzle seems to me to this part of the response:
>
> > I think the UniqueKeys may need to be changed from using
> > EquivalenceClasses to use Exprs instead.
>
> But I can't say I'm being overly helpful by pointing that out, since I
> don't have my head in the code enough to understand how you'd
> accomplish that :)
>
>
There was a dedicated thread [1] where David explain his idea very
detailed,
and you can also check that messages around that message for the context.
hope it helps.
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