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DB2 - Problembeschreibung
| Problem IC88353 | Status: Geschlossen |
QUERY RE-WRITER UNEXPECTEDLY RE-WRITES A BAD PERFORMANCE SQL | |
| Produkt: | |
DB2 FOR LUW / DB2FORLUW / A10 - DB2 | |
| Problembeschreibung: | |
Equality join predicates may be pushed down thru an OLAP
function. The columns in the join predicates are required to be
a superset of a unique index (or a primary key). The join
predicates then will form a correlation, resulting in limiting
the only join method eligible be the NLJOIN. This could cause a
performance degradation.
An indicator that a user has hit this problem is to look at the
Optimized Statement of the db2exfmt output.
(SELECT ..., <func>(<col> OVER (PARTITION NY <col>,...), ...
FROM Q#3, ...
WHERE Q#3.<col> = Q#2.<col>
) AS Q#1,
<table> AS Q#2, ...
If a correlated join predicate such as Q#3.<col> = Q#2.<col> is
seen and self-join of the base table with unique key as:
FROM K.R46C AS Q3, K.R05C AS Q4,
K.R05C AS Q5, K.R41C AS Q6,
K.R01C AS Q7,
the Q4 and Q5 are quantifiers over the same base table.
This SQL statement may hit this problem. | |
| Problem-Zusammenfassung: | |
**************************************************************** * USERS AFFECTED: * * DB2 UDB Version 10.2 * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to Version 10.1 FixPack 2. * **************************************************************** | |
| Local-Fix: | |
| verfügbare FixPacks: | |
DB2 Version 10.1 Fix Pack 2 for Linux, UNIX, and Windows | |
| Lösung | |
Problem was first fixed in DB2 UDB Version 10.1 FixPack 2. | |
| Workaround | |
keiner bekannt / siehe Local-Fix | |
| Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 17.11.2012 19.12.2012 19.12.2012 |
| Problem behoben ab folgender Versionen (IBM BugInfos) | |
| Problem behoben lt. FixList in der Version | |
| 10.1.0.2 |
|
| 10.5.0.2 |
|