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IT26278: INDEXES ON COLUMN-ORGANIZED TABLES ARE NOT CHOSEN FOR SOME TYPESOF SQL STATEMENTS

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APAR status

  • Closed as program error.

Error description

  • There are some situations where indexes on column-organized
    tables can provide significant performance improvements but they
    are not chosen by the optimizer.
    
    For example:
    create table tc1 (pk1 int not null, pk2 int not null, c1 int, c2
    int, c3 int) organize by column;
    create unique index tc1pk on tc1 (pk1,pk2);
    
    select * from tc1 where exists (
    select c1 from tc1 g where g.pk1 = tc1.pk1
    group by pk1,c1 having count_big(*) >= 1000)
    order by pk1,pk2;
    
    Index TC1PK  might've been a faster way to access table TC1 in
    the EXISTS subquery, depending on the data characteristics.
    
    The issue tends to occur when the potential index access occurs
    in sub-selects or sub-queries.
    

Local fix

  • Use an optimization guideline to force the desired index access.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 11.1 Mod 4 Fixpack 4 or higher                *
    ****************************************************************
    

Problem conclusion

  • First fixed in Db2 11.1 Mod 4 Fixpack 4
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT26278

  • 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

    2018-09-13

  • Closed date

    2018-11-27

  • Last modified date

    2018-11-27

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

  • 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

  • RB10 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":"11.1","Edition":"","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
27 November 2018