On Sun, Mar 06, 2005 at 10:38:22PM +0200, Ioannis Theoharis wrote: > in case that one has a table R(att0 int4, att1 int4), an index on att1 > and a query selecting only att1 whith a range condition over att1, then > the optimal access path for a rdbms would be "INDEX ONLY SCAN", which means > scan only the index, and not the relation (all the needed information > exists in index, because the select clause has only the att1 attribute). > This access path is selected in this case by Oracle. > > As far as i can see, postgresql select a simple "INDEX SCAN using index" > on table. That's because the index does not hold all the information. So INDEX ONLY is impossible. > Is there any tuning that one has to do, in order to make postgresql's > optimizer to select "INDEX ONLY SCAN" ? > Or postgresql doesn't support this feature at all? Nope. There's been discussion, but I wouldn't hold my breath. -- 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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