| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: crash-safe visibility map, take five |
| Date: | 2011-06-23 22:18:50 |
| Message-ID: | BANLkTimGkPyQ8VvAJLscYP0=ZbiSE+ooWg@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Wed, Jun 22, 2011 at 10:40 PM, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> 1. Torn pages -- not a problem because it's a single bit and idempotent.
Right.
> 2. PD_ALL_VISIBLE bit makes it to disk before a WAL record representing
> an action that makes the page all-visible. Depending on what action
> makes a page all-visible:
> a. An old snapshot is released -- not a problem, because if there is a
> crash all snapshots are released.
> b. Cleanup action on the page -- not a problem, because that will
> create a WAL record and update the page's LSN before setting the
> PD_ALL_VISIBLE.
Lazy VACUUM is the only thing that makes a page all visible. I don't
understand the part about snapshots.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Jeff Davis | 2011-06-23 22:40:53 | Re: crash-safe visibility map, take five |
| Previous Message | Robert Haas | 2011-06-23 21:40:33 | Re: spinlock contention |