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IT32009: Basic predicate "DECFLOAT != BIGINT" results in poor query performance

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APAR status

  • Closed as program error.

Error description

  • A query may perform poorly if it includes a predicate of the
    form DECFLOAT != BIGINT.  For example:
    
         CREATE TABLE T1(DECFLOAT DECFLOAT(16), I INT);
         CREATE TABLE T2(I INT);
         CREATE VARIABLE BIGINT BIGINT;
    
         SELECT * FROM T1
         WHERE EXISTS (SELECT * FROM T2 WHERE T1.I=T2.I)
           AND T1.DECFLOAT != BIGINT;
    
    Normally, the correlated EXISTS predicate would be transformed
    into a join to improve performance.  However, the predicate "
    T1.DECFLOAT != BIGINT" prevents the optimization.
    

Local fix

  • Multiply the BIGINT by DECFLOAT(1)
    
         SELECT * FROM T1
         WHERE EXISTS (SELECT * FROM T2 WHERE T1.I=T2.I)
           AND T1.DECFLOAT != (BIGINT * DECFLOAT(1));
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 v11.1.4.6                                     *
    ****************************************************************
    

Problem conclusion

  • First fixed in Db2 v11.1.4.6
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT32009

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2020-02-26

  • Closed date

    2021-03-17

  • Last modified date

    2021-03-17

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

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

    IT35065

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • RB10 PSN

       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":"11.1","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
04 May 2022