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Hello, On my system, the estimated query cost has huge difference with the real query cost. For example, a simple select query, the estimated query cost is 100X bigger than real cost, I think I need to calibrate the cost model parameters below(I still use default value) #seq_page_cost = 1.0 # measured on an arbitrary scale #random_page_cost = 4.0 # same scale as above #cpu_tuple_cost = 0.01 # same scale as above #cpu_index_tuple_cost = 0.005 # same scale as above #cpu_operator_cost = 0.0025 # same scale as above I googled it, and only find some suggestions, for example set random_page_cost to 1 or 2 for SSD, however, there is no doc about how to calibrate the cost model parameters to make the estimated query cost close to the real query cost. Thanks, James |
