| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | 高健 <luckyjackgao(at)gmail(dot)com> |
| Cc: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: What is the relationship between checkpoint and wal |
| Date: | 2013-08-23 03:30:09 |
| Message-ID: | 20130823033008.GF10710@eldon.alvh.no-ip.org |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
高健 escribió:
> ...
> Checkpoints are fairly expensive, first because they require writing out
> all currently dirty buffers, and second because they result in extra
> subsequent WAL traffic as discussed above.
> ...
>
> What confused me is that: (checkpoint)result in extra subsequent WAL
> traffic as discussed above...
>
> I haven't found any more information can describe it in the "above" of that
> page.
It means that the first change following the checkpoint that affects any
particular page will require a full page image of that page to be
written to WAL. See the discussion in the preceding paragraph about
"full_page_writes". It's not the checkpoint itself that writes this
extra WAL, but the rest of the system.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Michael Paquier | 2013-08-23 04:07:55 | Re: Temp files on Commit |
| Previous Message | 高健 | 2013-08-23 03:00:28 | What is the relationship between checkpoint and wal |