DB2 - Problembeschreibung
Problem IC99122 | Status: Geschlossen |
PERFORMANCE COULD BE POOR WHEN A SMALL NICKNAME JOINS A LARGE NICKNAME JOIN RESULT | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 | |
Problembeschreibung: | |
Performance could be poor when a small table joins a large table join result, e.g. select * from small_nick a, (select * from large_nick1 ln1, large_nick2 ln2 where ln1.c = ln2.c) b where a.c = b.c where the join of ln1 and ln2 generates a large result set. The bad performance can be resulted from Optimizer fails to generate a optimal plan. This is because, the optimal plan is a NLJN with the large table as the inner side, and the join predicate is pushdown to remote server with a FILTER under SHIP of inner side to filter data fetched as much as possible, that is: NLJN / \ SHIP SHIP | | a FILTER / \ large_nick1 large_nick2 However, due to limitation of Optimizer, a plan with the join predicate above the SHIP will be chosen, such a poor plan could be like: NLJN / \ SHIP TBSCAN <---join predicate is included here, right above the SHIP | | a TEMP | SHIP | FILTER .... / \ large_nick1 large_nick2 With such poor plan, all data from the two large nickames will be fetched, causing bad performance. | |
Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * Users who use Federation Server v10.5 * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to Federation Server v10.5 fp4 or above * **************************************************************** | |
Local-Fix: | |
verfügbare FixPacks: | |
DB2 Cancun Release 10.5.0.4 (also known as Fix Pack 4) for Linux, UNIX, and Windows | |
Lösung | |
The problem is fixed in v10.5 fp4 | |
Workaround | |
keiner bekannt / siehe Local-Fix | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 03.02.2014 08.09.2014 08.09.2014 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
Problem behoben lt. FixList in der Version | |
10.5.0.4 |