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DB2 - Problembeschreibung

Problem IC65934 Status: Geschlossen

QUERY PERFORMANCE MAY DEGRADE IN PRESENCE OF NON-EQUALITY PREDIC ATE ON
MORE THAN ONE TABLE THAT CAN BE REWRITTEN TO ONE TABLE

Produkt:
DB2 FOR LUW / DB2FORLUW / 910 - DB2
Problembeschreibung:
Query performance may degrade if it contains an non-equality 
predicate which references more than one table, but which can be 
rewritten to reference only one table using equivalence. 
 
Conditions required for such a scenario are: 
- Two or more tables referenced in a query 
- An non-equality predicate that references two or more tables 
(NONEQPRD) 
- Column equivalence via one or more equi-joins that makes it 
possible to rewrite NONEQPRD to reference only one table 
 
A trivial query that can be used to demonstrate this is: 
SELECT * 
FROM   T1, T2, T3 
WHERE  T1.C1 = T2.C1 
AND    T3.C2 = T2.C2 
AND    (T1.C1 = 'abcd' OR T3.C2 = 1 OR T2.C3 = 5)
Problem-Zusammenfassung:
**************************************************************** 
* USERS AFFECTED:                                              * 
* EE or EEE                                                    * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description.                                       * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 Version 9.1 Fix Pack 9 or later.              * 
****************************************************************
Local-Fix:
Manually rewrite any problematic non-equality predicates to 
their 
semantically equivalent forms for a single table. 
For the query above, this can be done like so: 
SELECT * 
FROM   T1, T2, T3 
WHERE  T1.C1 = T2.C1 
AND    T3.C2 = T2.C2 
AND    (T2.C1 = 'abcd' OR T2.C2 = 1 OR T2.C3 = 5)
verfügbare FixPacks:
DB2 Version 9.1 Fix Pack 9  for Linux, UNIX and Windows
DB2 Version 9.1 Fix Pack 10  for Linux, UNIX and Windows
DB2 Version 9.1 Fix Pack 11  for Linux, UNIX and Windows
DB2 Version 9.1 Fix Pack 12  for Linux, UNIX and Windows

Lösung
First fixed in DB2 Version 9.1 Fix Pack 9.
Workaround
keiner bekannt / siehe Local-Fix
Weitere Daten
Datum - Problem gemeldet    :
Datum - Problem geschlossen :
Datum - der letzten Änderung:
28.01.2010
19.04.2010
19.04.2010
Problem behoben ab folgender Versionen (IBM BugInfos)
9.1.FP9
Problem behoben lt. FixList in der Version
9.1.0.9 FixList