Donald Dong <xd...@csumb.edu> writes: > I find the cost from cheapest_total_path->total_cost is different > from the cost from queryDesc->planstate->total_cost. What I saw was > that GEQO tends to form paths with lower > cheapest_total_path->total_cost (aka the fitness of the children). > However, standard_join_search is more likely to produce a lower > queryDesc->planstate->total_cost, which is the cost we get using > explain.
> I wonder why those two total costs are different? If the total_cost > from the planstate is more accurate, could we use that instead as the > fitness in geqo_eval? You're still asking us to answer hypothetical questions unsupported by evidence. In what case does that really happen? regards, tom lane