There's a quite nice description in the docs: http://www.postgresql.org/docs/9.0/interactive/row-estimation-examples.html and a some more details for indexes: http://www.postgresql.org/docs/9.0/interactive/index-cost-estimation.html A bit more info about how this is used is available in this presentation: http://momjian.us/main/writings/pgsql/internalpics.pdf But if you need more details, then I quess the best approach to get it is to read the sources (search for the cost estimation etc.). regards Tomas Dne 10.4.2011 20:22, Radhya sahal napsal(a): > Dear ,all > i would to ask you about how postgresql optimizer parameters :- > 1- random page cost > > 2- cpu tuple cost > > 3- cpu operator cost > > 4- cpu index tuple cost > > 5- effective cache size > > play as parameters in cost estimator equation > > i imagine that cost function is the same as > > f(x,y,z,....)=ax+by...... > > cost(cpu tuple cost,cpu operator cost,....) > > can any one help me to know the equation that cost estimator used it.. > > My regard > > Radhya,,,, > > > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
