On Sat, Jan 15, 2005 at 04:00:03PM -0500, Edmund Dengler wrote: > Greetings! > > I have a technical question concerning multi-column indexes and their > implementation. I tried looking for the answr in the docs but couldn't > find anything. <snip> > I guess it breaks down to how these indexes are implemented. Are > multi-column indexes implemented as true multiple level indexes, in the > sense there is a level 1 index on <host_luid>, pointing to a level 2 index > on <log_luid>, pointing to a level 3 index on <luid>? Or are they the > equivalent of a <host_luid,log_luid,luid> single index (ie, as if I > created a functional index consisting of > host_luid || ',' || log_luid || ',' || luid > )? It's a true multi-column index, so it'll go straight to the right host_luid, then the log_luid and then start scanning. My guess is that your problem is that there are lots of rows that match but have a non-NULL error. Are you suffering from index bloat? As a suggestion, if (error IS NULL) is something you search on regularly and is a small portion of the table you should create a partial index: CREATE INDEX ... WHERE error IS NULL; Hope this helps, -- 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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