That would then depend on your server. If nothing really changes your server could plan the first run and re-use that plan each time. I know I can do that with

That would then depend on your server. If nothing really changes your server could plan the first run and re-use that plan each time. I know I can do that with Postgres, your server may be different. To figure out what the actual percentage is postgres has the ability to tell you how long it takes to plan a query so I would say try that. I wouldn't hazard a guess since its going to depend on too many factors and its so easy to just find out from the planner.