Re: FETCH FIRST clause PERCENT option

Thank you for the notification, Tomas.

At Thu, 16 Jan 2020 22:33:58 +0100, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote in
> This patch is marked as RFC since September. Since then there was no
> discussion on this thread, but Andrew proposed an alternative approach
> based on window functions in a separate thread [1] (both for this and
> for the WITH TIES case).
>
> I'll set this patch back to "needs review" - at this point we need to
> decide which of the approaches is the right one.

Even consdiering that we have only two usage , WITH TIES and PERCENT,
of the mechanism for now, I like [1] for the generic nature,
simpleness and smaller invasiveness to executor. The fact that cursor
needs materialize to allow backward scan would not be a big problem.
It seems that PERCENT will be easily implemented on that.

However, isn't there a possibility that we allow FETCH FIRST x PERCENT
WITH TIES, though I'm not sure what SQL spec tells about that? I
don't come up right now how to do that using window functions..

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center