Postgres doesn't alott (as far as I know) the planner a maximum amount of time. Rather, it picks the algorithm to use based on the number of joins. The computa

Postgres doesn't alott (as far as I know) the planner a maximum amount of time. Rather, it picks the algorithm to use based on the number of joins. The computational complexity of the default algorithm used by the query optimizer depends on the number of joins, and will explode if the number of joins gets high. Thus, if the number of joins exceeds a certain value (the default is 12), it will switch to use the genetic query optimizer (GEQO) [1], which uses genetic algorithms to randomly search towards an optimal plan. GEQO isn't constrained by time, either, but programmed with a maximum number of generations. [1] http://www.postgresql.org/docs/9.0/static/geqo.html http://www.postgresql.org/docs/9.0/static/geqo.html