| From: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Julien Rouhaud <rjuju123(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Marc Cousin <cousinmarc(at)gmail(dot)com> |
| Subject: | Re: Avoid full GIN index scan when possible |
| Date: | 2020-01-14 22:56:47 |
| Message-ID: | CAPpHfdtvW-jdRjJuiUHhG1GjXc4VianKoxHMzPXb203FKiW+kg@mail.gmail.com |
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On Wed, Jan 15, 2020 at 1:47 AM Alexander Korotkov
<a(dot)korotkov(at)postgrespro(dot)ru> wrote:
> I also had concerns about how excludeOnly keys work with lossy pages.
> I didn't find exact error. But I've added code, which skips
> excludeOnly keys checks for lossy pages. They aren't going to exclude
> any lossy page anyway. So, we can save some resources by skipping
> this.
I also found the way we combine lossy pages and exact TIDs pretty
asymmetric. Imagine one scan key A matches a lossy page, while
another key B have set of matching TIDs on the same page. If key A
goes first, we will report a lossy page. But if key B goes first, we
will report a set of TIDs with recheck set. It would be nice to
improve. But this is definitely subject of a separate patch.
------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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