Re: [HACKERS] Patch: Write Amplification Reduction Method (WARM)
| От | Pavan Deolasee |
|---|---|
| Тема | Re: [HACKERS] Patch: Write Amplification Reduction Method (WARM) |
| Дата | |
| Msg-id | CABOikdP+PrqVrKeVSPb2M5kT9r0wmpsPuicserbJKJ6eG1vRCg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [HACKERS] Patch: Write Amplification Reduction Method (WARM) (Bruce Momjian <bruce@momjian.us>) |
| Ответы |
Re: [HACKERS] Patch: Write Amplification Reduction Method (WARM)
|
| Список | pgsql-hackers |
On Thu, Feb 23, 2017 at 11:53 PM, Bruce Momjian <bruce@momjian.us> wrote:
On Thu, Feb 23, 2017 at 03:03:39PM -0300, Alvaro Herrera wrote:
> Bruce Momjian wrote:
>
> > As I remember, WARM only allows
> > a single index-column change in the chain. Why are you seeing such a
> > large performance improvement? I would have thought it would be that
> > high if we allowed an unlimited number of index changes in the chain.
>
> The second update in a chain creates another non-warm-updated tuple, so
> the third update can be a warm update again, and so on.
Right, before this patch they would be two independent HOT chains. It
still seems like an unexpectedly-high performance win. Are two
independent HOT chains that much more expensive than joining them via
WARM?
insert new index entry *only* in affected index. That itself does a good bit for performance.
So to answer your question: yes, joining two HOT chains via WARM is much cheaper because it results in creating new index entries just for affected indexes.
Thanks,
Pavan
Pavan Deolasee http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
PostgreSQL Development, 24x7 Support, Training & Services
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