DB2 - Problembeschreibung
Problem IT28286 | Status: Geschlossen |
POSSIBLE PERFORMACE REGRESSION FOR SELECT DISTINCT SUB-QUERY WHEN MIGRATING TO DB2 V11.1.3 | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / B10 - DB2 | |
Problembeschreibung: | |
If a query contains a sub-query with SELECT DISTINCT together with other complex operations such as OUTER JOIN and UNION ALL, the query performance might be regressed. Example query: SELECT t3.c4 FROM (SELECT t1.c2 FROM t1 LEFT OUTER JOIN t2 ON t1.c1 = t2.c1) AS v1(c2), t3 WHERE v1.c2 = t3.c1 AND t3.c3 IN (SELECT DISTINCT c3 FROM t3 WHERE c2 = 100) In v11.1.3, the SELECT DISTINCT sub-query is merged into the outer query block and DISTINCT is executed as part of the outer SELECT clause. Prior to V11.1.3, the sub-query is not merged and DISTINCT is executed as part of the sub-query. | |
Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * ALL * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to Db2 11.1 Mod 4 Fixpack 5 or higher * **************************************************************** | |
Local-Fix: | |
Workaround: Apply the following registry setting using the optimization guideline to the affected queries: /* */ | |
Lösung | |
Workaround | |
keiner bekannt / siehe Local-Fix | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 04.03.2019 16.01.2020 16.01.2020 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
Problem behoben lt. FixList in der Version |