|
Problem IC95491
|
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: |
|
| Local Fix: |
db2set DB2_ANTIJOIN=NO -im |
| available fix packs: |
DB2 Version 10.5 Fix Pack 3 for Linux, UNIX, and Windows
DB2 Version 10.5 Fix Pack 3a for Linux, UNIX, and Windows
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 |
|
| Workaround |
not known / see Local fix |
| Comment |
Upgrade to DB2 version 10.5.0.3 |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 27.08.2013
01.04.2014
01.04.2014 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 10.5.0.3
|
 |
| 10.5.0.3
|
|
| 10.5.0.4
|
|
