Re: wCTE behaviour

On Sun, Nov 14, 2010 at 11:02:08PM +0100, Yeb Havinga wrote:
> On 2010-11-14 21:06, Marko Tiikkaja wrote:
> >On 2010-11-14 8:51 PM +0200, Yeb Havinga wrote:
> >>On 2010-11-14 19:35, Robert Haas wrote:
> >>>On Sun, Nov 14, 2010 at 1:01 PM, Marko Tiikkaja
> >>><marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> wrote:
> >>>>In my opinion, all of these should have the same effect:
> >>>>DELETE all rows
> >>>>from "foo". Any other option means we're going to have
> >>>>trouble predicting
> >>>>how a query is going to behave.
> >>>I think it's clear that's the only sensible behavior.
> >>What if CTE's ever get input parameters?
> >
> >What about input parameters?
> With input parameters there is a clear link between a CTE and a
> caller. If a CTE is called more than once, it must be executed more
> than once, e.g. (notation t:x means cte has parameter x)
>
> WITH t:x AS (INSERT INTO foo VALUES(x) RETURNING *)
> SELECT (SELECT * FROM t(1)), (SELECT * FROM t(2));
> runs the cte two times, hence two new rows in foo.

I think we can worry about that if we ever have run-time functions
done as WITH, but I think they'd be a *much* better fit for DO.

Cheers,
David.
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