| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Petr Jelinek <petr(at)2ndquadrant(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Indirect indexes |
| Date: | 2016-10-20 15:27:07 |
| Message-ID: | CAGTBQpazf9nwdn7i-BjTr28H-b0e6eU3eoo_qQUzFtLvnWBY5g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Oct 20, 2016 at 12:14 PM, Petr Jelinek <petr(at)2ndquadrant(dot)com> wrote:
> WARM can do WARM update 50% of time, indirect index can do HOT update
> 100% of time (provided the column is not changed), I don't see why we
> could not have both solutions.
>
> That all being said, it would be interesting to hear Álvaro's thoughts
> about which use-cases he expects indirect indexes to work better than WARM.
I'm not Alvaro, but it's quite evident that indirect indexes don't
need space on the same page to get the benefits of HOT update (even
though it wouldn't be HOT).
That's a big difference IMO.
That said, WARM isn't inherently limited to 50%, but it *is* limited
to HOT-like updates (new tuple is in the same page as the old), and
since in many cases that is a limiting factor for HOT updates, one can
expect WARM will be equally limited.
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