| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(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 14:21:14 |
| Message-ID: | 20170321142114.dh674kyr4lx26hof@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Robert Haas wrote:
> On Tue, Mar 21, 2017 at 10:01 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > Sure, we can try that. I think we need to try it with
> > synchronous_commit = off, otherwise, WAL writes completely overshadows
> > everything.
>
> synchronous_commit = off is a much more realistic scenario than fsync = off.
Sure, synchronous_commit=off is a reasonable case. But I say if we lose
a few % on the case where you update only the first indexed of a large
number of very wide columns all indexed, and this is only noticeable if
you don't write WAL and only if you update all the rows in the table,
then I don't see much reason for concern.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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