On Mon, Feb 07, 2005 at 11:07:16AM -0800, TJ O'Donnell wrote: > I understand the value of indexes and of ANALYZE for the efficient use of > them. > In the following statement, you can see that the index scan is being used. > Even though it takes 80 seconds (for a 1.25 million row table), it is > much faster than without the index. > But, if I repeat this search, it speeds up by more than a factor of 2! > I love it, but I'd sure like to understand why. When I do it a third time, > it speeds up again. A fourth try does not speed it up more. > Is this speedup due to some memory/disk buffering from which I'm > benefiting? I'm using linux (actually under VMware on WinXP, so it's even Yep. Buffering improves performance considerably. > less > efficient that it could be on it's own). Or is the planner learning > something from previous runs of this search? It appears not, since the > rows it thinks it needs to search are the same in the EXPLAIN ANALYZE > outputs below. Can someone help me understand why my searches are speeding > up so I can make it happen the first time, if possible? Nope, the plan would be the same everytime. There's no way the planner is doing anything different. -- 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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