| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, 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: | 2017-02-23 18:45:24 |
| Message-ID: | 20170223184524.icdwoh34txoob2ja@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Bruce Momjian wrote:
> Well, let's walk through this. Let's suppose you have three updates
> that stay on the same page and don't update any indexed columns --- that
> would produce a HOT chain of four tuples. If you then do an update that
> changes an indexed column, prior to this patch, you get a normal update,
> and more HOT updates can be added to this. With WARM, we can join those
> chains
With WARM, what happens is that the first three updates are HOT updates
just like currently, and the fourth one is a WARM update.
> and potentially trim the first HOT chain as those tuples become
> invisible.
That can already happen even without WARM, no?
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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