Teodor Sigaev <teodor@sigaev.ru> writes:
>> to use it when the AM can't guarantee to return the same sequence of
>> tuples after backing up. So I think it would be sufficient to have
>> gistmarkpos et al throw error if called.
> Why not to remove gistrestrpos/gistmarkpos/ginrestrpos/ginmarkpos from pg_am table?
First, because that would mean adding code to the indexam.c functions to
avoid crashing, and second because then we'd have to force initdb to
change our minds about this. I think having stub functions that throw
errors, rather than no catalog entry at all, is cheap future-proofing.
regards, tom lane