Donald Dong <xdong@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