DB2 FOR LUW / DB2FORLUW / A50 - DB2

DB2 optimizer might not match a string literal with values in 
distribution stats in some rare cases. The problem can happen on 
CHAR() or VARCHAR() data type columns only, and when the 
following conditions are met: 
 
- The length of the literal is greater than 33 
- The high2key and low2key values of the column have a common 
prefix, and the length of the common prefix is greater than 25. 
- The length of literal is 8 bytes or more greater than the 
length of the common prefix 
 
For example: 
 
A table contains the following data, and distribution statistics 
are collected. 
 
- 10 rows of value 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef11111111' 
-   1 row of value 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef22222222' 
-   1 row of value 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef33333333' 
-   1 row of value 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef44444444' 
 
query: select * from mytable where c = 
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef11111111' 
 
DB2 optimizer might not be able to match the literal in the 
query with the frequent values. As a result, it might estimate 
inaccurate cardinality: 
 
      Rows 
     RETURN 
     (   1) 
      Cost 
       I/O 
       | 
        1 
     TBSCAN 
     (   2) 
     10.0244 
        1 
       | 
       13 
 TABLE: DB2INST1 
     MYTABLE 
       Q1

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* USERS AFFECTED:                                              * 
* ALL                                                          * 
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* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
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* RECOMMENDATION:                                              * 
* Upgrade to DB2 Version 10.5 Fixpack 5.                       * 
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First fixed in Version 10.5 Fixpack 5.

not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

10.06.2014
18.03.2015
18.03.2015