Re: MOVE LAST: why?

Hiroshi Inoue <Inoue@tpf.co.jp> writes:
> I'm suspicios if we should implement scrollable cursors
> with the combination of the current MOVE and FETCH implemen-
> tation. For example the backwards FETCH operation for group
> nodes isn't implemented properly yet(maybe).

Yeah, backwards scan is not implemented for quite a large number of plan
node types :-(.  I am not sure that it is practical to fix them all.
I have been toying with the notion of making cursors on complex plans
safe for FETCH BACKWARD by sticking a MATERIAL node atop the plan, if
the top plan node isn't one that can handle backwards scan.

The trouble with this of course is that one of the main things people
like to use cursors for is huge result sets, and materializing those is
the last thing you want to do :-(
        regards, tom lane