Re: Incorrect cursor behaviour with gist index

> Seems like a lotta work for a partial solution :-(.  Probably the path
> of least resistance is to teach the planner that only some index AMs can
> do backwards scan.  That would result in a Materialize buffer getting
> placed in front of the query if the user demanded scroll capability,
> but it would cost nothing in the more typical case where backwards scan
> isn't needed.

Probably, it will be a better solution. In this case GiST code could be 
simplified - remove support of backward scan (in any case not fully workable)

> 
> It should be sufficient to specify this in pg_am, right?  Or could the
> opclass or indexkey details affect it?

I don't see any examples where it depends on opclass or index key, that's is a 
AM property.

> 
> BTW, can GIN do backwards scan?
No, at all.

-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
  WWW: http://www.sigaev.ru/