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Problem IC67741
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Status: Closed |
POSSIBLE INCORRECT RESULTS OPTIMIZING A <COLUMN> = ? PREDICATE ON A UNION ALL VIEW USED AS A COMMON SUB-EXPRESSION |
| product: |
DB2 FOR LUW / DB2FORLUW / 950 - DB2 |
| Problem description: |
Incorrect results may occur during the optimization of a Union
All view (UA) that is used as a common sub-expression (CSE) and
has predicate(s) applied on it.
The conditions for such a scenario are:
1) Query contains a UA (UA1) over another UA (UA2) and UA2 is
used in both legs of UA1 (making it a CSE)
2) The legs of UA2 are simple selects over base-tables (BT)
3) The legs of UA2 have no predicates or simple equi-join or
range-join local predicates
4) Each BT used in UA2 has equi-join check constraints defined
on it
5) Either leg of UA1 has one or more <column> = ? predicate
(PARAMPRD)
6) The column referenced in PARAMPRD is an output column of UA2
7) All column(s) referenced in PARAMPRD(s) source directly from
BTs and have equi-join check constraints defined on them
8) The parameter marker referenced in PARAMPRD is bound to a
value VAL1.
9) VAL1 is different from the check constraint value of the
column from the largest BT under UA2 that is referenced in
PARAMPRD |
| Problem Summary: |
Users Affected: Specific to a union all view used as a common
sub-expression.
Problem Description: POSSIBLE INCORRECT RESULTS OPTIMIZING A
<COLUMN> = ? PREDICATE ON A UNION ALL VIEW USED AS A COMMON
SUB-EXPRESSION
Problem Summary: See above. |
| Local Fix: |
Lower the query optimization class to a value less than 5. This
can be done either by altering the CURRENT QUERY OPTIMIZATION
special register or by altering the DFT_QUERYOPT database
configuration parameter. |
| available fix packs: |
DB2 Version 9.5 Fix Pack 6a for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 10 for Linux, UNIX, and Windows
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| Solution |
Problem was first fixed in Version 9.5 FixPak 6 |
| Workaround |
Lower the query optimization class to a value less than 5. This
can be done either by altering the CURRENT QUERY OPTIMIZATION
special register or by altering the DFT_QUERYOPT database
configuration parameter. |
| BUG-Tracking |
forerunner : APAR is sysrouted TO one or more of the following: IC68260 IC68261
follow-up : |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 08.04.2010
07.10.2010
07.10.2010 |
| Problem solved at the following versions (IBM BugInfos) |
9.5.
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| Problem solved according to the fixlist(s) of the following version(s) |
