Currently the top-20 shapes benchmark runs each query exactly once before changing index configurations. This prevents the plancache from providing any help in lowering execution time.

It would be helpful to include an option for this benchmark to run the queries multiple times to take into account the benefit of the plancache.

For many of these queries, there is only 1 solution, but we should still include plancache metrics (probably from explain()) so that we can track planning time independently of execution time.