Subquery not working in 11g

Question

Hi all,
We have an 11.1.0.7 instance on SLES10. And when we run following sql, it crashes.
select decode(sum(pos),0,'H',decode(sum(hareket),0,'P','T')) from
(select count(1) pos,0 hareket from cost.pos_hareket p where
p.onay_eh='E' and p.is_merkez_kod='70' and
p.tarih>='28.04.2011'
union
select 0,count(1) from otel.hareket h where h.tarih>='28.04.2011' and
h.is_merkezi_kod='70' and h.belge_no not in (select
p.belge_no from cost.pos_hareket p where p.onay_eh='E' and
p.is_merkez_kod='70' and p.tarih>='28.04.2011' union select
o.belge_no from otel.onburo_manuel_extra o where
o.is_merkez_kod='70'));
But when we run following sql, it is ok.
select decode(sum(pos),0,'H',decode(sum(hareket),0,'P','T')) from
(select count(1) pos,0 hareket from cost.pos_hareket p where
p.onay_eh='E' and p.is_merkez_kod='70' and
p.tarih>='28.04.2011'
union
select 0,count(1) from otel.hareket h where h.tarih>='28.04.2011' and
h.is_merkezi_kod='70' and (h.belge_no not in (select
p.belge_no from cost.pos_hareket p where p.onay_eh='E' and
p.is_merkez_kod='70' and p.tarih>='28.04.2011') or h.belge_no not in (select
o.belge_no from otel.onburo_manuel_extra o where
o.is_merkez_kod='70')));

Answer 1

ilke_altinpulluk wrote:
the query hold up very very long time.In that case the obvious thing to do would (normally) be to run the faster query.
In your case I am not keen on suggesting this as the two queries don't appear to be logically equivalent.
They are hard to read in the form you've posted but one appears to be:
select ....
where something not in (
    select ...
    union
    select ...
)While the second is:
select ....
where something not in (
    select ...
or something not in (
    select ...
)If my interpretation is correct, then that OR should be an AND for the queries to be logically the same.
In the absence of any further information, I think it's likely that the first query is able to unnest the subquery, while the second query has to operate the two subqueries as filter subqueries - and the nature of your data, indexing, etc. makes one plan much more efficient than the other.
You could try an /*+ no_unnest */ hint in the subquery of the first query to see what impact that might have.
Regards
Jonathan Lewis