Re: Cost-based Optimizers

> Hi, > > Its worth looking at the techie manuals for V6.* and above as these > give a reasonable explanation of the costs / histograms that > informix has in its optimiser, as far as I am aware this is > just as powerful as Ingres's if not more so with various > confidence levels the optimiser can see on the histograms > of the data. > > Graham Twaddle > Technical Director > Beta Computers (Europe) Ltd > beta@cix.compulink.co.uk > > A friend in need is usually on the net ! I would like to add my two pennorth on this one. The optimizers in both Ingres and INFORMIX use histograms that are updated by update statistics. When I last heard any comments on Ingres concerning this it was stated that the optimizer was fast but that update statistics took a few hours to complete. In all of these cases it is worh remembering that the update statistics time should be considered as part of the performancecharacteristics of the optimizer.