DB2 - Problembeschreibung
Problem IC61598 | Status: Geschlossen |
THE DB2 QUERY OPTIMIZER MAY UNDERESTIMATE THE JOIN COST, POTENTIALLY LEADING TO A SUB-OPTIMAL QUERY ACCESS PLAN | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 | |
Problembeschreibung: | |
If your SQL statement contains an equality join predicate between two tables, such as the one in the WHERE clause in the following example . SELECT ... FROM T1, T2 ... WHERE ... T1.COLUMN1 = T2.COLUMN2 ... . and distribution statistics are collected, the optimizer could take advantage of the distribution statistics in combination with the high2key and low2key statistics during join cost computation. . If the number of distinct values in either COLUMN1 or COLUMN2 is less than 3, then the optimizer may underestimate the cost of the join. . The number of distinct values is described by the COLCARD column in the SYSSTAT.COLUMNS catalog view. | |
Problem-Zusammenfassung: | |
see APAR text. | |
Local-Fix: | |
1) Use an optimizer profile to force the desired access plan, OR 2) Update the LOW2KEY of the column with the smaller number of distinct values to the LOW2KEY of the column with the higher number of distinct values. | |
verfügbare FixPacks: | |
DB2 Version 9.7 Fix Pack 1 for Linux, UNIX, and Windows | |
Lösung | |
Problem first fixed in DB2 UDB 9.7 Fixpack 1. | |
Workaround | |
see APAR text | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 19.06.2009 04.02.2010 04.02.2010 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
9.7.FP1 | |
Problem behoben lt. FixList in der Version | |
9.7.0.1 |