On Wed, Mar 02, 2005 at 11:30:58PM +0200, Ioannis Theoharis wrote: > On Wed, 2 Mar 2005, Martijn van Oosterhout wrote: > > What makes you think that? Clustering is nice, but postgresql needs to > > get the right answer and that the table in clustered is not something > > postgresql can rely on. > > If postgresql doesn't rely on it, it' s postgresql's technical decision > (and i don't know the reason) and not a default decision between rdbms's. > > But if you know exactly the reason, it would be a great help for me to > know it. Easy, if you CLUSTER a table, it's CLUSTERed then. But it doesn't stay that way. As soon as you insert a new row, or update an old one, it gets added to the end (the only place with space) and now it's not clustered anymore. It's almost clustered and from a caching point of view it's fine. But postgresql can't assume at any point a table will stay clustered, an insert could happen in the middle of your processing. Logically you can't magically add space in the middle of a file, you have to move everything else up. If you know an efficient way to keep a table clustered while handling arbitrary inserts and updates, I'd be curious to know... -- Martijn van Oosterhout <kleptog@xxxxxxxxx> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
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