|
Problem IC95490
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Status: Closed |
QUERY WITH NOT EXISTS PREDICATES MIGHT HAVE PERFORMANCE DEGRADATION |
| product: |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 |
| Problem description: |
Under rare scenarios, DB2 might produce a sub-optimal query plan
if the following conditions are satisfied:
1. There are 3 or more inner joined tables in the query (say T1,
T2, T3)
2. The query contains a Not Exists or Not In subquery
3. One of the tables (T1) in the inner join is also the source
for the subquery.
4. There is only a single join predicate between Table T1 and
one of the other tables (T2)
5. There are local predicates on tables not directly connect to
T1.
eg. select * from t1, t2, t3 where
t1.c1 = t2.c1 and t2.c2 = t3.c2 and t3.c1 = 1 and
not exists (select c1 from T4 where t1.c2 = t4.c2); |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* All *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Please upgrade to DB2 Cancun Release 10.5.0.4 *
**************************************************************** |
| Local Fix: |
db2set DB2_ANTIJOIN=NO -im |
| available fix packs: |
DB2 Cancun Release 10.5.0.4 (also known as Fix Pack 4) for Linux, UNIX, and Windows
DB2 Version 10.5 Fix Pack 9 for Linux, UNIX, and Windows
|
| Solution |
Fixed in DB2 Cancun Release 10.5.0.4 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 27.08.2013
03.11.2014
03.11.2014 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 10.5.0.4
|
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