DB2 - Problembeschreibung
Problem IT01998 | Status: Geschlossen |
Performance may be poor for queries having an OUTER JOIN and 3 or more table in the FROM clause | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 | |
Problembeschreibung: | |
Queries containing an OUTER JOIN and at least three other tables in the from clause may experience poor performance in some scenarios. Typically the two tables referenced in the OUTER JOIN will be large tables without any predicates for local filtering and the query will contain a series of joins involving at least 3 tables each using different join columns. None of the tables joined to the OUTER JOIN will contain local predicates. An example of such query is: SELECT * FROM T1, T2, T3, T4, T5, T6 LEFT OUTER JOIN T7 ON T6.c5 = T7.c5 WHERE T1.c4 = T2.c4 AND T2.c3 = T3.c3 AND T3.c1 = T4.c1 AND T4.c2 = T5.c2 AND T5.c2 = T6.c2 AND T1.c4 = ? There is a linear sequence of joins from T1 to T6 which is referenced in the outer join. The only filtering is on T1. | |
Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * ALL * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to DB2 version 10.5 Fix Pack 7 or higher. * **************************************************************** | |
Local-Fix: | |
Rewrite the query: SELECT * FROM T1 INNER JOIN T2 ON T1.c4 = T2.c4 INNER JOIN T3 ON T2.c3 = T3.c3 INNER JOIN T4 ON T3.c1 = T4.c1 INNER JOIN T5 ON T4.c2 = T5.c2 INNER JOIN T6 ON T5.c2 = T6.c2 LEFT OUTER JOIN T7 ON T6.c5 = T7.c5 WHERE T1.c4 = ? | |
Lösung | |
Problem first fixed in DB2 version 10.5 Fix Pack 7. | |
Workaround | |
keiner bekannt / siehe Local-Fix | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 23.05.2014 28.01.2016 28.01.2016 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
Problem behoben lt. FixList in der Version | |
10.5.0.7 |