DB2 - Problembeschreibung
Problem IC78195 | Status: Geschlossen |
DB2 OPTIMIZER CAN ESTIMATE A TOO SMALL IO COST WHEN RANGE PREDICATES ARE APPLIED BY AN IXSCAN | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / 950 - DB2 | |
Problembeschreibung: | |
When a range predicate or an equality predicate that is applied by an IXSCAN is preceded by another range predicate, DB2 optimize can estimate a too small IO cost. The problem is more likely to occur when the range predicate involves parameter marks or host variables. For example, assume we have the following index create index idx1 on t1 (c1, c2) Further assume we have predicates c1 <= ? and c1 >=? and c2 = 'a' If these predicates are applied by an IXSCAN on idx1, then the IO cost estimation of the IXSCAN can be too small. This can result in sub-optimal query plans. In db2exfmt output, one can observe the following: 1.93755e+06 IXSCAN ( 6) 19622.5 3 | 1.93755e+08 INDEX: SCHM1 IDX1 Note that the number of rows out of the IXSCAN is 1.93755e+06, but the number of IOs is only 3. | |
Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * All Platforms * **************************************************************** * PROBLEM DESCRIPTION: * * DB2 OPTIMIZER CAN ESTIMATE A TOO SMALL IO COST WHEN RANGE * * PREDICATES ARE APPLIED BY AN IXSCAN * **************************************************************** * RECOMMENDATION: * * Upgrade to DB2 v9.5 Fixpack 9 or higher * **************************************************************** | |
Local-Fix: | |
verfügbare FixPacks: | |
DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows | |
Lösung | |
First Fixed in DB2 v9.5 Fixpack 9 | |
Workaround | |
keiner bekannt / siehe Local-Fix | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 18.08.2011 07.03.2012 07.03.2012 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
9.5.FP9 | |
Problem behoben lt. FixList in der Version | |
9.5.0.9 |