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IC69294: ENHANCE QUERY PERFORMANCE THROUGH PUSHDOWN OF JOIN(S) THROUGH DISJOINT UNION ALL VIEW(S)

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error 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.
    

Local fix

  • Manually rewrite any applicable queries to be of the form
    derived through this enhancement.
    

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                                               *
    ****************************************************************
    

Problem conclusion

  • Upgrade to FP7
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC69294

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    950

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2010-06-16

  • Closed date

    2011-01-10

  • Last modified date

    2011-01-10

  • APAR is sysrouted FROM one or more of the following:

    IC69007

  • APAR is sysrouted TO one or more of the following:

    IC71543

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R950 PSY

       UP

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Document Information

Modified date:
10 January 2011