Re: wCTE behaviour

On Nov 11, 2010, at 9:29 AM, Tom Lane wrote:

>> I can see that, but if one can't see the result of the write, or can't determine whether or not it will be visible
inadvance, what's the point of writeable CTEs? 
>
> The writeable CTE returns a RETURNING set, which you can and should use
> in the outer query.  The thing that is being argued about here is what
> you see if you look "directly" at the target table rather than making
> use of RETURNING.  Essentially, I'm arguing that we shouldn't promise
> any particular behavior at that level, just as we don't promise that
> UPDATE updates different rows in any determinate order.

Yes, if RETURNING guarantees the execution order, then great. That was the first thing I tried to do before I realized
thatthe current CTE implementation doesn't support w. 

David