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IT31132: DB2 OPTIMIZER INCORRECTLY RECOMMENDS AN INDEX AS PREREQUISITE FOR ZIGZAG-JOIN

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • When running a query that qualifies for a zigzag join, it is
    possible that the explain format information suggests to add
    indexes in order to be able to run zigzag join as part of the
    access plan even though an index might already fulfill this
    request.
    
    A message similar to the following will be put out:
    
    Extended Diagnostic Information:
    --------------------------------
    
    Diagnostic Identifier: 1
    Diagnostic Details: EXP0039I Query complexity measure. Highest
    number
    of joins in any query block: "6".
    Diagnostic Identifier: 2
    Diagnostic Details: EXP0256I Analysis of the query shows that
    the
    query might execute faster if an additional index
    was created to enable zigzag join. Schema name:
    "RUW_APP ". Table name: "TABLENAME". Column list:
    "(COLUMN1, COLUMN2)".
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * all                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 11.5 m3 fp0 or later                          *
    ****************************************************************
    

Problem conclusion

  • Upgrade to Db2 11.5 m3 fp0 or later
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT31132

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B50

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2019-12-03

  • Closed date

    2020-04-24

  • Last modified date

    2020-04-24

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

    IT31125

  • 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

  • RB50 PSY

       UP

[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSEPGG","label":"DB2 for Linux- UNIX and Windows"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"11.5","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
17 December 2021