DB2 - Problembeschreibung
| Problem IT01796 | Status: Geschlossen |
OPTIMIZER COMPUTES INCORRECT CARDINALITY ESTIMATE IN PRESENCE OF STATISTICAL VIEW WITH A PREDICATE THAT HAS AN EXPRESSION | |
| Produkt: | |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 | |
| Problembeschreibung: | |
The optimizer might compute an incorrect cardinality estimate in
an access plan for a SQL statement on which a statistical view
is eligible, if the following conditions are true:
1) There is a statview ( sv1 ), whose SELECT list contains
expression column.
2) There is another statview ( sv2 ), which contains a predicate
involving the same expression.
For example, consider the following statistical views:
create view sv1(x) as (select c1+5 from t1);
create view sv2(y) as (select c1 from t1 where c2+1 < 2 and c1+5
= 5);
Please note the expression 'c1+5'. It is the output column of
sv1 and it is also used in predicate for sv2. In this case, the
optimizer might compute an incorrect cardinality estimate for
the following SQL statement:
select * from t1 where c1+5=5 and c2+1<2;
The explain plan ( i.e. db2exfmt output ) of above SQL may show
the following diagnostic messages:
Diagnostic Details: EXP0233I The predicate "Q4.C1 + 5 = 5"
contains
an expression matching the statistical
view column
"SCHEMA1.SV1"
Diagnostic Details: EXP0147W The following statistical view
was used
by the optimizer to estimate
cardinalities:
"SCHEMA1"."SV2". | |
| Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * ALL * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to DB2 Version 10.5 Fix Pack 4 * **************************************************************** | |
| Local-Fix: | |
| verfügbare FixPacks: | |
DB2 Cancun Release 10.5.0.4 (also known as Fix Pack 4) for Linux, UNIX, and Windows | |
| Lösung | |
Upgrade to DB2 Version 10.5 Fix Pack 4 | |
| Workaround | |
keiner bekannt / siehe Local-Fix | |
| Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 14.05.2014 27.10.2014 27.10.2014 |
| Problem behoben ab folgender Versionen (IBM BugInfos) | |
| Problem behoben lt. FixList in der Version | |
| 10.5.0.4 |
|