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Problem IC87878
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Status: Closed |
DB2 QUERY OPTIMIZER MIGHT CHOOSE A NON-OPTIMAL ACCESS PLAN FOR QUERIES INVOLVING JOINS ON SKEWED DATA |
| product: |
DB2 FOR LUW / DB2FORLUW / A10 - DB2 |
| Problem description: |
This is an extension to IC71258. You might encounter this
problem if your SQL statement is not performing optimally, one
or more joins in the query are on columns with significant skew
in one side of the join, one of the columns in the join is
unique, but the non-unique side of the join covers a larger
domain of values. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* All Platforms *
****************************************************************
* PROBLEM DESCRIPTION: *
* This is an extension to IC71258. You might encounter this *
* problem if your SQL statement is not performing optimally, *
* one *
* or more joins in the query are on columns with significant *
* skew *
* in one side of the join, one of the columns in the join is *
* unique, but the non-unique side of the join covers a larger *
* domain of values. *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 Version 10 Fixpack 2. *
**************************************************************** |
| Local Fix: |
As described in IC71258, to solve this problem, a statistical
view can be created on the join, where applicable, to provide
the optimizer the appropriate information to account for the
skew. |
| available fix packs: |
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
|
| Solution |
The fix will be included in DB2 Version 10 Fixpack 2. |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 04.11.2012
31.12.2012
31.12.2012 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 10.1.0.2
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 |
| 10.5.0.2
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