Re: "Compacting" a relation
От | Hannu Krosing |
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Тема | Re: "Compacting" a relation |
Дата | |
Msg-id | 1164796140.3527.14.camel@localhost.localdomain обсуждение исходный текст |
Ответ на | "Compacting" a relation (Peter Eisentraut <peter_e@gmx.net>) |
Ответы |
Re: "Compacting" a relation
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Список | pgsql-hackers |
Ühel kenal päeval, K, 2006-11-29 kell 11:19, kirjutas Peter Eisentraut: > vacuumlazy.c contains a hint "Consider compacting this relation" but AFAICT, > there is no indication anywhere how "compacting" is supposed to be achieved. > I guess this means VACUUM FULL or CLUSTER, but I don't think the hint can be > processed effectively by a user. I once had an online/concurrent/non-locking compacting script, which did for each const_pk_col_with_largest_ctid staring starting from end of relation UPDATE rel SET pk_col=pk_col WHERE pk_col = const_pk_col_with_largest_ctid until the tuple moved to another page as determined by SELECT ctid FROM rel where pk_col=const_pk_col_with_largest_ctid if the tuple moved to a larger page number then it was time for another lazy vacuum. this compacted the live data in the table and if done enough times, the lazy vacuum did actually shorten the file. -- ---------------- 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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