Jan Wieck wrote:
>
> > rule system will be able to put _any_ VIEW' query into
> > FROM clause...
>
> Possible - but IMHO the wrong thing to do. As it is now for a
"Will be able" doesn't mean "will DO" -:))
I just said that subqueries in FROM will resolve all
problems with aggregates in VIEWs.
> If we put any view into a subquery RTE, we force the planner
> to materialize the view and do a nestloop over t3 and
^^^^^^^^^^^
Do you mean creating some tmp table etc?
No - it's not required.
> materialized v1 where possibly using t1 or t2 as the
> outermost scanrelation would be better.
SELECT t3.a, v1.b, v1.c
FROM t3,
(SELECT t1.a, t1.b, t2.c FROM t1, t2 WHERE t1.a = t2.a) v1
WHERE t3.a = v1.a;
can be planned as
Nestloop
SubPlan
...what is costless for subquery...
Seq/Index scan on t3
- no materialization...
On the other hand, as we talk about query optimization - why
rule system should do optimizer' work? Why not just put
_any_ VIEW' query into FROM and let optimizer decide
could query be rewritten as join or not? Ppl do strange
things sometimes -:) Sometimes they use subqueries in
WHERE while joins could be used and our optimizer don't
try to catch this. I know that Sybase does.
And, imho, we should implement this ... sometime -:))
Vadim
