| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Patch: Write Amplification Reduction Method (WARM) |
| Date: | 2017-03-21 10:56:54 |
| Message-ID: | CAA4eK1JeAp3g0-X8X0U87UW3YjNKG3qxR-0-xCTUY=mxT4aOag@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Mar 9, 2017 at 8:43 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, Mar 8, 2017 at 2:30 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
>> Not really -- it's a bit slower actually in a synthetic case measuring
>> exactly the slowed-down case. See
>> https://www.postgresql.org/message-id/CAD__OugK12ZqMWWjZiM-YyuD1y8JmMy6x9YEctNiF3rPp6hy0g@mail.gmail.com
>> I bet in normal cases it's unnoticeable. If WARM flies, then it's going
>> to provide a larger improvement than is lost to this.
>
> Hmm, that test case isn't all that synthetic. It's just a single
> column bulk update, which isn't anything all that crazy, and 5-10%
> isn't nothing.
>
> I'm kinda surprised it made that much difference, though.
>
I think it is because heap_getattr() is not that cheap. We have
noticed the similar problem during development of scan key push down
work [1].
[1] - https://commitfest.postgresql.org/12/850/
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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