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 | |
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 |