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DB2 - Problembeschreibung

Problem IC84597 Status: Geschlossen

DB2 SQL Optimizer might choose a suboptimal access plan for query with
'OPTIMIZE FOR N ROWS' clause and IS NULL predicate

Produkt:
DB2 FOR LUW / DB2FORLUW / A10 - DB2
Problembeschreibung:
For a query with an 'optimize for N rows' clause and a highly 
filtering IS NULL predicate, the DB2 SQL Optimizer might choose 
a suboptimal query access plan as in the following example: 
 
select * 
from fact left outer join d1 on f1 = id1 
          left outer join d2 on f2 = id2 
          left outer join d3 on f3 = id3 
          left outer join d4 on f4 = id4 
where d3.c31 is null; 
 
with access plan graph for this query ( db2exfmt output ): 
 
                                        RETURN 
                                          | 
                                        >HSJOIN 
                                 /--------+---------\ 
                             >HSJOIN                TBSCAN 
                       /-------+-------\              | 
                   >HSJOIN             TBSCAN         D4 
                 /---+----\              | 
             FILTER       TBSCAN         D2 
               |            | 
            >HSJOIN         D1 
         /-----+------\ 
     TBSCAN           TBSCAN 
       |                | 
      FACT              D3 
 
The IS NULL predicate is applied by the FILTER.  The MAXPAGES 
argument described in the details of the TBSCAN operator(s) 
below the FILTER is a potential indicator of the problem.  If 
the MAXPAGES argument is small and the IS NULL predicate is 
filtering many records, then a large amount of synchronous IO 
might be required, resulting in suboptimal performance.
Problem-Zusammenfassung:
**************************************************************** 
* USERS AFFECTED:                                              * 
* ALL                                                          * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 version 10.1 Fix Pack 1                       * 
****************************************************************
Local-Fix:
verfügbare FixPacks:
DB2 Version 10.1 Fix Pack 1 for Linux, UNIX, and Windows
DB2 Version 10.1 Fix Pack 2 for Linux, UNIX, and Windows
DB2 Version 10.1 Fix Pack 3 for Linux, UNIX, and Windows
DB2 Version 10.1 Fix Pack 4 for Linux, UNIX, and Windows
DB2 Version 10.1 Fix Pack 3a for Linux, UNIX, and Windows
DB2 Version 10.1 Fix Pack 6 for Linux, UNIX, and Windows

Lösung
Problem was first fixed in DB2 version 10.1 Fix Pack 1
Workaround
keiner bekannt / siehe Local-Fix
Weitere Daten
Datum - Problem gemeldet    :
Datum - Problem geschlossen :
Datum - der letzten Änderung:
14.06.2012
31.10.2012
31.10.2012
Problem behoben ab folgender Versionen (IBM BugInfos)
Problem behoben lt. FixList in der Version
10.1.0.1 FixList
10.5.0.1 FixList