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IC83850: DB2 QUERY OPTIMIZER MIGHT CHOOSE A NON-OPTIMAL ACCESS PLAN FOR QUERIES INVOLVING JOINS ON SKEWED DATA

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error 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.
    

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.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 Version 9.7 Fix Pack 7                        *
    ****************************************************************
    

Problem conclusion

  • Problem was first fixed in Version 9.7 Fix Pack 7
    

Temporary fix

  • See Local Fix
    

Comments

APAR Information

  • APAR number

    IC83850

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    970

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-05-30

  • Closed date

    2012-11-20

  • Last modified date

    2012-11-20

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

    IC81077

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

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R970 PSN

       UP



Document information

More support for: DB2 for Linux, UNIX and Windows

Software version: 9.7

Reference #: IC83850

Modified date: 20 November 2012