"Wappler, Robert" <rwappler@ophardt.com> writes:
> Attached is a query and its corresponding plan, where sorting of the CTE
> acts seems to be the bottle neck. It is a real execution plan captured
> with the auto_explain module.
There isn't a lot of intelligence about CTEs at the moment; in
particular I don't believe we have any provision for recognizing that
the output of a CTE is already sorted by anything the outer query would
recognize. The CTE is just a black box as far as the upper plan is
concerned.
In principle it's doable, I think, but nobody's spent much effort on
CTE optimization yet.
regards, tom lane