On Tue, Dec 26, 2006 at 12:04:40PM -0500, D'Arcy J.M. Cain wrote: > I have been testing this statement and find that it seems not quite > true. Although ctid changes on update, VACUUM FULL does not change it. > What it does do is make lower areas available again so an update after a > VACUUM FULL can reuse lower numbers rather than higher ones before.
A VACUUM FULL will try to compact a table. Thus if there's a lot of free space at the beginning, it will move tuples near the end to the beginning. > Now it certainly seems to me that it should behave as described given > the definition of VACUUM FULL so I am a little confused by my tests. > My test table only has two entries in it. Is that the issue? In fact, > I find the same behaviour if I do a simple VACUUM on the table. On a table with two entries, VACUUM FULL is going to do nothing of interest. Moving tuples within a page is useless, generally. Have a nice day, -- Martijn van Oosterhout <firstname.lastname@example.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to > litigate.
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