| From: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
|---|---|
| To: | 9erthalion6(at)gmail(dot)com |
| Cc: | florisvannee(at)Optiver(dot)com, pg(at)bowt(dot)ie, jesper(dot)pedersen(at)redhat(dot)com, david(dot)rowley(at)2ndquadrant(dot)com, tomas(dot)vondra(at)2ndquadrant(dot)com, alvherre(at)2ndquadrant(dot)com, thomas(dot)munro(at)gmail(dot)com, jtc331(at)gmail(dot)com, rafia(dot)pghackers(at)gmail(dot)com, jeff(dot)janes(at)gmail(dot)com, bhushan(dot)uparkar(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org, a(dot)korotkov(at)postgrespro(dot)ru |
| Subject: | Re: Index Skip Scan |
| Date: | 2020-02-06 12:22:20 |
| Message-ID: | 20200206.212220.642002310227620136.horikyota.ntt@gmail.com |
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| Lists: | pgsql-hackers |
At Thu, 6 Feb 2020 11:57:07 +0100, Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote in
> > On Thu, Feb 06, 2020 at 10:24:50AM +0900, Kyotaro Horiguchi wrote:
> > At Wed, 5 Feb 2020 17:37:30 +0100, Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote in
> > We could add an additional parameter "in_cursor" to
> > ExecSupportBackwardScan and let skip scan return false if in_cursor is
> > true, but I'm not sure it's acceptable.
>
> I also was thinking about whether it's possible to use
> ExecSupportBackwardScan here, but skip scan is just a mode of an
> index/indexonly scan. Which means that ExecSupportBackwardScan also need
> to know somehow if this mode is being used, and then, since this
> function is called after it's already decided to use skip scan in the
> resulting plan, somehow correct the plan (exclude skipping and try to
> find next best path?) - do I understand your suggestion correct?
I didn't thought so hardly, but a bit of confirmation told me that
IndexSupportsBackwardScan returns fixed flag for AM. It seems that
things are not that simple.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
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