Re: My tests show that a WITH HOLD cursor has subtly different semantics from a WITHOUT HOLD cursor

IIUC, all you've demonstrated here is the (sometimes) case for the WITHOUT HOLD cursor where a cache is not used (i.e., the typical case).  In this situation the executor, when asked to rewind back to the beginning, goes and restarts execution at the beginning (executor nodes form a tree, it is probable that certain nodes are more efficient at this "start over" thing that others - e.g., I suspect a materialize node sitting in the tree would prevent a sequential scan node from being asked to "start over"), which necessarily involves potentially re-evaluating volatile functions/expressions as noted.

David J.