IC90465: PERFORMANCE DEGRADATION MIGHT BE NOTICED WITH NOT EXISTS SUBQUERY WITH MULTIPLE TABLES.

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • Under some scenarios, DB2 might choose a suboptimal plan if the
    following conditions are true:
    1. The query has a not exists subquery
    2. The subquery contains 2 or more base tables
    3. The correlated join predicate in the subquery has an index on
    the join column.
    

Local fix

  • Disable AntiJoin by either :
    1>  db2set DB2_ANTIJOIN=NO -im
    2>  set up an optimization guideline to disable the antijoin for
    this specific query only.
    

Problem summary

  • Under some scenarios, DB2 might choose a suboptimal plan if the
    following conditions are true:
    1. The query has a not exists subquery
    2. The subquery contains 2 or more base tables
    3. The correlated join predicate in the subquery has an index on
    the join column.
    

Problem conclusion

  • First fixed in DB2 Version 10.1 Fix Pack 3.
    

Temporary fix

  • Disable AntiJoin by either :
    1>  db2set DB2_ANTIJOIN=NO -im
    2>  set up an optimization guideline to disable the antijoin for
    this specific query only.
    

Comments

APAR Information

  • APAR number

    IC90465

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-02-25

  • Closed date

    2014-05-06

  • Last modified date

    2014-05-06

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

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

    IC95335

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • RA10 PSY

       UP



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Document information


More support for:

DB2 for Linux, UNIX and Windows

Software version:

10.1

Reference #:

IC90465

Modified date:

2014-05-06

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