|
Problem IC69294
|
Status: Closed |
ENHANCE QUERY PERFORMANCE THROUGH PUSHDOWN OF JOIN(S) THROUGH DISJOINT UNION ALL VIEW(S) |
| product: |
DB2 FOR LUW / DB2FORLUW / 950 - DB2 |
| Problem description: |
DB2 Query ReWrite may be able to improve the performance of a
query by optimizing it during compilation if it satisfies the
following conditions:
- The query refers to 3 or more UNION ALL views (UAV)
- Each UAV branch or operand is a select over a base table or
nickname
- The UAVs all have the same number of branches or operands
- The UAVs are all joined to each other
- The joins between the UAVs are either all inner joins or joins
on columns that source from row-preserving sides of any outer
joins
- At least one join column from each branch or operand of each
UAV has the same local predicate as corresponding branches from
other UAVs
- A one-to-one join mapping can be derived from all of the
previous conditions
This enhancement is only available under registry variable
control. To enable it, issue:
db2set
DB2_UNION_OPTIMIZATION=[<other-values>,]COMPLEX_DISJOINT_UA_JPPD
[,<other-values>]
and restart the database manager for settings to take effect. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* NA *
****************************************************************
* PROBLEM DESCRIPTION: *
* DB2 Query ReWrite may be able to improve the performance of *
* a *
* query by optimizing it during compilation *
****************************************************************
* RECOMMENDATION: *
* Upgrade to FP7 *
**************************************************************** |
| Local Fix: |
Manually rewrite any applicable queries to be of the form
derived through this enhancement. |
| available fix packs: |
DB2 Version 9.5 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 10 for Linux, UNIX, and Windows
|
| Solution |
Upgrade to FP7 |
| Workaround |
not known / see Local fix |
| BUG-Tracking |
forerunner : APAR is sysrouted TO one or more of the following: IC71543
follow-up : |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 16.06.2010
10.01.2011
10.01.2011 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.1.0.7
|
 |
| 9.5.0.7
|
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