Tom Lane wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> > Tom Lane wrote:
> >> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> >>> Won't this cause issues to MergeAppend optimizations?
>
> >> Like what?
>
> > Well, as I understand, MergeAppend needs to know the sort order of the
> > child node, right? But that's available only on the relation RTE, not
> > on the colstore-join RTE.
>
> Uh, what? Sort order is a property of a path, not an RTE.
Evidently need to do more digging .. but that makes plenty of sense.
> And we have always understood which join types preserve sort order.
That's obvious now that you say it.
> You misunderstood the thrust of my comment, which basically is that
> I doubt anyone will think that rejecting that combination is an
> acceptable implementation restriction. It might be all right if it
> doesn't work very well in v0, but not if the implementation is designed
> so that it can never be fixed.
Gotcha.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services