Re: cursors: SCROLL default, error messages

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> Neil Conway <neilc(at)samurai(dot)com> writes:
> > On Fri, 2003-03-21 at 12:12, Tom Lane wrote:
> >> (No problem here with adding the noise-word option, of course.)
>
> > Note that it won't be a noise word: if NO SCROLL is specified, an
> > attempt to do a backward fetch on a non-scrollable cursor will yield an
> > error.

Does the spec *require* an error, or merely say that backward fetches aren't
required to work?

Most specs don't impose many restrictions on what happens if the user does non
conformant things. The SQL spec is a bit, er, nonstandard in that respect, but
even for it I'm a bit surprised that it would explicitly say that if NO SCROLL
is specified that backward fetches have to produce an error.

The only possible rationale I could see for the spec imposing that kind of
restriction would be a security concern if an middleware layer allocates a NO
SCROLL cursor, pages forward, and then allows an upper tier to do unrestricted
operations on that cursor trusting the database not to allow scrolling back.

--
greg