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IT26127: NON-PUSHDOWNABLE HASH JOIN ELIGIBLE PREDICATES INVOLVING NICKNAMES MAY BE USED SUB-OPTIMALLY

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APAR status

  • Closed as program error.

Error description

  • Hash join eligible predicates that involve nicknames may be
    applied as a residual predicate when they cannot be pushed down
    into a federated datasource.
    
        For example:
    
        CREATE TABLE T (C1 CHAR(10), ...);
        CREATE NICKNAME N FOR FEDSERVER.MYSCHEMA.T2;
        ALTER  NICKNAME N ALTER COLUMN C1 LOCAL TYPE CHAR(15);
    
        SELECT * FROM T, N WHERE TRIM(N.C1) = T.C1;
    
        If the predicate cannot be pushed down through the federated
    datasource, the query rewrite engine should generate an
    additional predicate ( in this case, TRIM(N.C1) = VARCHAR(T.C1,
    15) ) to be used as a hash join predicate for quicker joining.
    If this new predicate is not created and the optimizer decides
    to use a hash join, it may apply the original predicate (
    TRIM(N.C1) = T.C1 ) as a residual which may be more expensive.
    

Local fix

  • N/A
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * all                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to 11.1.4.7                                          *
    ****************************************************************
    

Problem conclusion

  • Upgrade to 11.1.4.7
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT26127

  • 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

    2018-08-30

  • Closed date

    2022-04-17

  • Last modified date

    2022-04-17

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

    IT26125

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

    IT39136 428AC7Ÿ IT39585

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