I wrote:
> Maybe we should redefine the API as involving a TupleTableSlot that
> the AM is supposed to fill --- basically, moving StoreIndexTuple
> out of the common code in nodeIndexonlyscan.c and requiring the AM
> to do that work. The possible breakage of third-party code is a
> bit annoying, but there can't be all that many third-party AMs
> out there yet.
After looking a bit at gist and sp-gist, neither of them would find that
terribly convenient; they really want to create one blob of memory per
index entry so as to not complicate storage management too much. But
they'd be fine with making that blob be a HeapTuple not IndexTuple.
So maybe the right approach is to expand the existing API to allow the
AM to return *either* a heap or index tuple; that could be made to not
be an API break.
regards, tom lane
