> how explian works as math equations to estimate cost with constatn query > parameters > such as cpu_tuple cost ,random page cost ...etc > i want maths expression in order to know how these parameters will effect > in cost ??? The expressions are complicated, and they are certainly not linear as you seem to think from your previous post. > please any one can help me ?? What do you need this for? If your goal is to optimize a real application, then you should just vary the cost parameters and measure the resulting change in query times. If your interests are academic, there were some excellent suggestions for places to start in response to your previous post. Best, Nathan -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
