Teodor Sigaev <teodor@sigaev.ru> writes:
>> Implementing the "replace these TIDs" operation atomically would be
>> simple, except for the new bitmap index am. It should be possible there
> That isn't simple (may be, even possible) from GIN.
I suspect that those pushing this idea only care about btrees anyway,
so one possible answer is that HOT is only possible when the table has
only btree indexes --- or at least, only indexes of AMs that support the
replace-these-TIDs operation. (Yet another pg_am flag...)
regards, tom lane