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IT17512: IN DB2 DPF, POSSIBLE WRONG RESULT WHEN OUTER JOIN PREDICATE COL1=COL2 AND BOTH COLUMNS ARE FROM THE OUTER TABLE

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APAR status

  • Closed as program error.

Error description

  • DB2 can return wrong query result when all of the following
    conditions are satisfied
    
    1. DPF (Data Partitioning Feature) environment.
    2. The query has a outer join, and the outer join has a
    predicate of the form COLUMN1=COLUMN2, where both columns are
    from the outer table.
    3. Either DB2COMPOPT=OJLOCALPRDPLANNING is set, or the
    NULL-producing side of the outer join is a CSE (Common
    SubExpression), UNION, GROUP-BY, or another outer join.
    4. The query has a key requirement or order requirement on one
    of the columns in the COLUMN1=COLUMN2 predicate.
    
    For example:
    
    The following query can possibly produce a wrong result in DPF
    environment, because the query has an outer join predicate of
    TT.T1_C1 = TT.T1_C2, the NULL-producing side of the outer join
    is another outer join, and the query requires "DISTINCT
    TT.T1_C2"
    
    SELECT DISTINCT TT.T1_C2 FROM T1 TT LEFT OUTER JOIN
    (SELECT T2.T2_C4 FROM T2 FULL OUTER JOIN T1 ON T1.T1_C1 =
    T2.T2_C2) TT2 on TT.T1_C1 = TT.T1_C2
    
    The following query can possibly produce a wrong result in DPF
    environment and when DB2COMPOPT=OJLOCALPRDPLANNING is set,
    because the query has an outer join predicate of
    T1.T1_C1=T1.T1_C2, and the query requires "ORDER BY TT.T1_C2"
    
    SELECT * FROM T2 TT1, (SELECT * FROM T1 LEFT JOIN T2 on
    T1.T1_C1=T1.T1_C2 ) TT
    WHERE TT1.T2_C4 = TT.T1_C1
    ORDER BY TT.T1_C2
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 10.5 Fix Pack 9 or higher                     *
    ****************************************************************
    

Problem conclusion

  • First fixed in Db2 10.5 Fix Pack 9
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT17512

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    A50

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-10-14

  • Closed date

    2017-09-29

  • Last modified date

    2017-10-12

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

    IT17458

  • 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

  • RA50 PSN

       UP

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSEPGG","label":"Db2 for Linux, UNIX and Windows"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"10.5","Edition":"","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
12 October 2017