Re: BUG #17445: "ON CONFLICT" has different behaviors when its param is passed with prepared stmt or hard coded

Peter Geoghegan <pg@bowt.ie> writes:
> On Mon, Mar 21, 2022 at 4:03 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Perhaps a specific error message would be worth the trouble.

> I'm not sure how difficult it would be offhand, so I can't commit to it now.

Searching that expression tree for an EXTERN Param surely wouldn't take
much code.  What's not clear to me though is whether that's the full
extent of problematic cases.  (Picking a user-friendly wording for the
error message might be hard too.)

            regards, tom lane