DB2 - Problembeschreibung
Problem IT07926 | Status: Geschlossen |
PERFORMANCE MAY BE POOR FOR QUERIES INVOLVING COLUMN ORGANIZED TABLE THAT ARE REFERENCED BY CARTESIAN JOIN PREDICATES | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 | |
Problembeschreibung: | |
Performance may be poor for queries involving COLUMN ORGANIZED table that are referenced by cartesian join predicates. Cartesian join predicates are typically present when each of the tables involved in the join have a local equality predicate with the same constant value. For example a query SELECT c1, c2 FROM T1, T2, T3 where T1.c1='A' and T2.d1 = 'A' and T1.c2=T3.e2 and T2.d3 = T3.e3 will have an cartesian join predicate 'T1.c1 = T2.d1', depending on the statistics present the optimizer may choose a plan where T1 is joined with T2 before T3. Examining the access plan produced by db2exfmt, affected queries will typically have a series of joins between tables and one or more of those HSJOINs will show an estimated cardinality that is larger then both of the estimated input cardinalities. For such a HSJOIN operator, the details will show the predicate with filter factor 1.0. There may also be a FILTER operator higher in the plan where a non-cartesian predicate between the same two tables is applied. | |
Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * ALL * **************************************************************** * PROBLEM DESCRIPTION: * * See Problem Description above. * **************************************************************** * RECOMMENDATION: * * Upgrade to DB2 Version 10.5 Fix Pack 6 * **************************************************************** | |
Local-Fix: | |
Use an optimization profile to force a different join order where the effectively cartesian join is delayed or where the order of the joins is swapped to allow the non-cartesian predicate to be applied early. | |
Lösung | |
First fixed in DB2 Version 10.5 Fix Pack 6. | |
Workaround | |
keiner bekannt / siehe Local-Fix | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 25.03.2015 01.09.2015 01.09.2015 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
Problem behoben lt. FixList in der Version | |
10.5.0.6 |