Martijn van Oosterhout wrote: > On Thu, Apr 26, 2007 at 12:13:13AM +0200, Listmail wrote: > > VACUUM FULL is slow because it plays with the indexes... > > CLUSTER is slow because it has to order the rows... > > And: > VACUUM FULL has to seek/read/write all over the disk to get it's job > done. > CLUSTER can scan through the table linearly a few times and write out > the result. > Now it's true that sorting large files involves overflowing to disk, > but that path has been pretty well optimised. Hmm, no, CLUSTER doesn't scan the table linearly; it uses an indexscan, so it also needs seek/read/seek/read/write. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc.
