|
Problem IT08268
|
Status: Closed |
DB2 MIGHT PERFORM POORLY FOR SUBQUERY CONTAINING CORRELATED SELECT LIST EXPRESSIONS AND COLUMN ORGANIZED TABLES |
| product: |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 |
| Problem description: |
Under rare scenarios, DB2 might produce a suboptimal plan if the
following conditions are true:
1) The query contains one or more subqueries
2) The subquery is either a NOT EXISTS subquery or of the form
EXISTS OR EXISTS
3) At least one subquery contains one or more column organized
tables
4) The subquery also contains a correlated reference to the
outer subselect in the select list expression
eg.
Select *
from T1
where EXISTS (select T1.c1
from T2
where T1.C1 = T2.C1) OR
EXISTS (select T3.c1
from T3
where T1.C1 = T3.C1) |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* All *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 version 10.5.0.7 *
**************************************************************** |
| Local Fix: |
Replace the correlated reference with constant 1 in the select
list.
Select *
from T1
where EXISTS (select 1
from T2
where T1.C1 = T2.C1) OR
EXISTS (select 1
from T3
where T1.C1 = T3.C1) |
| Solution |
Fixed in DB2 version 10.5.0.7 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 13.04.2015
05.02.2016
05.02.2016 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 10.5.0.7
|
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