Re: Revitalising VACUUM FULL for 8.3
От | Hannu Krosing |
---|---|
Тема | Re: Revitalising VACUUM FULL for 8.3 |
Дата | |
Msg-id | 1172752971.3216.21.camel@localhost.localdomain обсуждение исходный текст |
Ответ на | Re: Revitalising VACUUM FULL for 8.3 (Hannu Krosing <hannu@skype.net>) |
Ответы |
Re: Revitalising VACUUM FULL for 8.3
Re: Revitalising VACUUM FULL for 8.3 |
Список | pgsql-hackers |
Ühel kenal päeval, N, 2007-03-01 kell 14:32, kirjutas Hannu Krosing: > If we can trust FSM, the whole process just becomes the backward scan > and null updates until the null update does not move tuple to a lower > page. Also, for the duration of COMPACT TABLE the updated tuple should > always be placed in lowes available slot, that is no same-page updates > should be tied before going to FSM. > > This has some downsides : > > 1 - the original xmin will be lost > > 2 - as with any updates, it may block/abort other concurrent updates, so > it could be a good thing to teach the update mechanism about null > updates. > > Still I think that this would be the chepest way to get VACUUM FULL > behaviour without locking the whole table for long time This means that VACUUM FULL mytable; would translate to: VACUUM mytable; -- make free space COMPACT mytable; -- move tuples in a bunch of small transactions -- might have a GUC for max trx length VACUUM mytable; -- free the tuples at the end and give space back to fs -- ---------------- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com
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