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DB2 - Problembeschreibung

Problem IC62285 Status: Geschlossen

INACCURATE CARDINALITY ESTIMATES FROM MULTIPLE ELIGIBLE STATISTICAL
VIEWS THAT HAVE DIFFERENT NUMBER OF PREDICATES

Produkt:
DB2 FOR LUW / DB2FORLUW / 970 - DB2
Problembeschreibung:
Description: 
When the statistics of multiple statistical views are used by 
the optimizer, some cardinality estimates may be inaccurrate, as 
in the following example where the statistics of two statisical 
views 
 
-- generic statistical view 
-- 
CREATE VIEW FACT_DIM_SV AS 
SELECT f.*, d.DIM_KEY d 
FROM  FACT f, DIM d 
WHERE f.DIM_KEY = d.DIM_KEY; 
 
-- specific statistical view for queries with d.code=10 local 
predicate 
-- 
CREATE VIEW FACT_DIM_SV2 AS 
SELECT f.*, d.DIM_KEY d 
FROM  FACT f, DIM d 
WHERE f.DIM_KEY = d.DIM_KEY 
AND d.code = 10; 
 
are used by the optimizer when compiling a query such as: 
 
SELECT SUM(f.amount), d.code 
FROM FACT f, DIM d 
WHERE f.DIM_KEY = d.DIM_KEY 
AND d.code = 10 
AND d.era = 1;
Problem-Zusammenfassung:
INACCURATE CARDINALITY ESTIMATES FROM MULTIPLE ELIGIBLE 
STATISTICAL VIEWS THAT HAVE DIFFERENT NUMBER OF PREDICATES
Local-Fix:
Cardinality estimates may improve if the generic statistical 
view is dropped.  However, queries that do not contain the 
predicates of the remaining specific statistic view will not 
benefit from its statistics.
verfügbare FixPacks:
DB2 Version 9.7 Fix Pack 1 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 2 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 3 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 3a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 4 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 5 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 6 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows

Lösung
Problem was first fixed in version 9.7 Fixpak 1
Workaround
Cardinality estimates may improve if the generic statistical 
view is dropped.  However, queries that do not contain the 
predicates of the remaining specific statistic view will not 
benefit from its statistics.
Weitere Daten
Datum - Problem gemeldet    :
Datum - Problem geschlossen :
Datum - der letzten Änderung:
31.07.2009
19.12.2009
19.12.2009
Problem behoben ab folgender Versionen (IBM BugInfos)
9.7.
Problem behoben lt. FixList in der Version
9.7.0.1 FixList