That is it possible to tell the planner that index is off limits i.e. don't ever generate a plan using it?
Rationale: Schema changes on big tables. I might have convinced myself / strong beliefs that for all queries that I need to be fast the planner does not need to use a given index (e.g. other possible plans are fast enough). However if I just drop the index and it turns out I'm wrong I might be in a world of pain because it might just take way to long to recreate the index.
I know that I can use pg_stat* to figure out if an index is used at all. But in the presense of multiple indices and complex queries the planner might prefer the index-to-be-dropped but the difference to the alternatives available is immaterial.
The current best alternative we have is to test such changes on a testing database that gets regularly restored from production. However at least in our case we simply don't know all possible queries (and logging all of them is not an option).