DB2 FOR LUW / DB2FORLUW / A10 - DB2

DB2 might not be able to fully optimize queries containing the 
following pattern leading to long execution times. 
Pattern conditions: 
1) The query contains one or more outer joins. 
2) The null producing side of the outer join is involved in a 
correlated predicate inside a subquery 
3) The subquery is of the form EXISTS or IN. 
4) The subquery is used in the context of a predicate with no 
complex expressions like OR, CASE, etc. 
 
eg. 
select * from t1 left join t2 on t1.c1 = t2.c1 where exists 
(select * from t3 where t2.c2 = t3.c2); 
select * from t1 left join t2 on t1.c1 = t2.c1 where t2.c2 in 
(select c2 from t3); 
 
 Workaround: 
Rewrite the query to convert the subquery into a DISTINCT inner 
join 
select * from t1 left join t2 on t1.c1 = t2.c1 inner join 
(select distinct c2 from t3) on t2.c2 = t3.c2

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* USERS AFFECTED:                                              * 
* ALL                                                          * 
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* PROBLEM DESCRIPTION:                                         * 
* See Problem Description above.                               * 
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* RECOMMENDATION:                                              * 
* Upgrade to DB2 Version 10.1 Fix Pack 5.                      * 
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First fixed in Version 10.1 Fix Pack 5.

not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

10.07.2014
14.07.2015
14.07.2015