Re: Sort is actually PlanState?

Hitoshi Harada <umi.tanuki@gmail.com> writes:
> I wonder why SortState is a ScanState. As far as I know ScanState
> means the node may need projection and/or qualification, or it scans
> some relation, but Sort actually doesn't do such things.

No, not really.  Per the comment for ScanState:
*        ScanState extends PlanState for node types that represent*        scans of an underlying relation.  It can
alsobe used for nodes*        that scan the output of an underlying plan node --- in that case,*        only
ScanTupleSlotis actually useful, and it refers to the tuple*        retrieved from the subplan.
 

It might be that we don't actually need ScanTupleSlot right now in the
implementation of Sort, but I don't see a good reason to remove the
field.  We might just have to put it back later.

BTW, Sort is not the only node type like this --- I see at least
Material that's not projection-capable but has a ScanState.
        regards, tom lane