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PI07823: TOTAL ESTIMATED COST FOR A QUERY WITH A COMMON TABLE EXPRESSION (CTE) MAY BE INACCURATE

A fix is available

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APAR status

  • Closed as program error.

Error description

  • For example, the total cost of the query did not accurately
    reflect the cost of executing the common table expression.  This
    could cause the total estimated cost of the query to be too low
    which could impact IDAA offloading or the predictive governor
    

Local fix

  • n/a
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: DB2 10 and 11 for z/OS users of common       *
    *                 table expressions (CTEs).                    *
    ****************************************************************
    * PROBLEM DESCRIPTION: The total cost of a query with common   *
    *                      table expressions may be                *
    *                      underestimated.                         *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The total cost of a query with common table expressions may be
    underestimated as the cost of materializing common table
    expressions may not be included in the total cost. This problem
    may prevent a query with common table expressions from being
    offloaded to IBM DB2 Analytics Accelerator.
    
    The cost estimation of a query can be checked in
    DSN_STATEMNT_TABLE and DSN_DETCOST_TABLE after EXPLAINing a
    query.
    
    Additional Keywords:
    SQLACCESSPATH  SQLEXPLAIN  SQLCTE  IDAAV2R1/K  IDAAV3R1/K
    IDAAV4R1/K  DSN_STATEMNT_TABLE  DSN_DETCOST_TABLE
    

Problem conclusion

  • Code has been modified to include the cost of materializing
    common table expressions in the total cost.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI07823

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-12-12

  • Closed date

    2014-01-16

  • Last modified date

    2014-02-05

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

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

    UI14308

Modules/Macros

  • DSNXOTS
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UI14308

       UP14/02/01 P F401

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.



Document information

More support for: DB2 for z/OS

Software version: A10

Reference #: PI07823

Modified date: 05 February 2014


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