DB2 - Problembeschreibung
Problem IC99234 | Status: Geschlossen |
IMPROVE QUERY PERFORMANCE WHEN QUERY CONTAINS CARTESIAN JOIN OVER SELECT DISTINCT FROM ALIAS | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 | |
Problembeschreibung: | |
A select distinct subquery may be consolidated to the outer query block by db2 compiler in sought of better join planning for the outer query block, although that postpones the duplicated rows removal of the subquery. But if the select distinct subquery result participates in no join predicate of the outer query block, i.e. this outer query has cartesian join, preserving select distinct to remove duplication before performing the cartesian join is a better plan. This heuristic used to be available to subquery "select distinct from base_table" and is now extended to subquery "select distinct from alias" | |
Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * ALL * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to V10.5 Fixpack 3 * **************************************************************** | |
Local-Fix: | |
Manually rewrite "select distinct col1, col2, ..., colN from alias" to "select col1, col2, ..., colN from alias group by col1, col2, ..., colN". | |
verfügbare FixPacks: | |
DB2 Cancun Release 10.5.0.4 (also known as Fix Pack 4) for Linux, UNIX, and Windows | |
Lösung | |
Upgrade to V10.5 Fixpack 3 | |
Workaround | |
keiner bekannt / siehe Local-Fix | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 07.02.2014 17.09.2014 17.09.2014 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
Problem behoben lt. FixList in der Version | |
10.5.0.4 |