|
Problem IC84002
|
Status: Geschlossen |
IMPROVE ACCURACY OF FILTER FACTOR ESTIMATE FOR NON-CORRELATED EXISTS CLAUSE |
| Produkt: |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 |
| Problembeschreibung: |
The filter factor of a non-correlated EXISTS clause, such as:
...
where
exists ( select 1 from table1 A, table2 B where A.key =
b.key and A.col2 = 'XYZ')
...
May be more or less filtering depending on the results of the
subselect in the exists. This APAR will improve the accuracy of
the resulting filter factor of the EXISTS clause.
For example, you may see the exists subselect show up in the
explain plan as a FILTER with an estimated cardinality of 0.5
instead of a more accurate estimate for the probability a row
will be returned from the subselect:
/---------+
0.5
FILTER
|
/-------+--------\
1 40
TBSCAN ^NLJOIN
| |
1 /-----+------\
TABFNC: SYSIBM 40 1
GENROW TBSCAN IXSCAN
Q4 | |
1000 1000
TABLE: DB2INST1 INDEX: DB2INST1
TABLE1 TABLE2_PK
Q2 Q1 |
| Problem-Zusammenfassung: |
****************************************************************
* USERS AFFECTED: *
* All *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 9.7 FP7 or subsequent fix pack *
**************************************************************** |
| Local-Fix: |
Use SELECTIVITY CLAUSE or Optimizer Profile to change the
overall access plan. |
| verfügbare FixPacks: |
DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows
|
| Lösung |
Problem First Fixed in DB2 Version 9.7 Fix Pack 7 |
| Workaround |
keiner bekannt / siehe Local-Fix |
| Weitere Daten |
Datum - Problem gemeldet :
Datum - Problem geschlossen :
Datum - der letzten Änderung:
| 07.06.2012
01.11.2012
01.11.2012 |
| Problem behoben ab folgender Versionen (IBM BugInfos) |
9.7.FP7
|
| Problem behoben lt. FixList in der Version |
| 9.7.0.7
|
 |
