Re: crash-safe visibility map, take five
| От | Robert Haas |
|---|---|
| Тема | Re: crash-safe visibility map, take five |
| Дата | |
| Msg-id | BANLkTimGkPyQ8VvAJLscYP0=ZbiSE+ooWg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: crash-safe visibility map, take five (Jeff Davis <pgsql@j-davis.com>) |
| Ответы |
Re: crash-safe visibility map, take five
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| Список | pgsql-hackers |
On Wed, Jun 22, 2011 at 10:40 PM, Jeff Davis <pgsql@j-davis.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
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