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IT35118: POSSIBLE WRONG RESULT WITH ALWAYS-FALSE PRED OR EXISTS PRED

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APAR status

  • Closed as program error.

Error description

  • When a query has always-false predicates or EXISTS predicates,
    we may get wrong results. More specifically, we may get more
    rows returned than anticipated.
    
    Another example with always-false predicates:
    
         create table t1 (c1 int);
         create table t2 (c1 int);
    
         insert into t1 values (5);
         insert into t2 values (5), (5);
    
         -- Bad query with "always false" predicate, should return 1
    row, returns 2
         select * from t1
         where ((t1.c1 < 1 and t1.c1 > 2 )    -- Always false
    predicate
                 or
                (exists(select * from t2 where t2.c1=t1.c1)));
    
         C1
         -----------
                   5
                   5
    
           2 record(s) selected.
    
         -- Same query without "always false" predicate, correctly
    returns 1 row
         select * from t1
         where exists(select * from t2 where t2.c1=t1.c1);
    
         C1
         -----------
                   5
    
           1 record(s) selected.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 version 11.1.4.6                              *
    ****************************************************************
    

Problem conclusion

  • Fixed in Db2 version 11.1.4.6
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT35118

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2020-12-01

  • Closed date

    2021-03-16

  • Last modified date

    2021-03-29

  • 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":"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