PM81848: INCORROUT (OUT OF ORDER BY SEQUENCE) ON QUERY WITH ORDER-BY AND PLAN CHOOSING HYBRID JOIN WITH SORTN_JOIN=N

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The output records may not be in the right Order By sequence
  on query with Order-by clause.  In such cases, it's Hybrid
  join plan with SORTN_JOIN=N being chosen.
  
  Additional Keywords: SQLINCORR SQLINCORROUT DB2INCORR/K
             SQLHYBRID SQLHYBRIDJOIN HYBRIDJOIN SQLORDERBY
  

Local fix

• Use HINT or add OPTIMIZE FOR 1 ROW to force an access plan
  other than Hybrid join.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of DB2 10 for z/OS who have        *
  *                 queries containing ORDER BY, GROUP BY, or    *
  *                 set function DISTINCT with an index matching *
  *                 the ORDER BY, GROUP BY, or set function      *
  *                 DISTINCT columns.                            *
  ****************************************************************
  * PROBLEM DESCRIPTION: Possible incorrect output for a         *
  *                      query containing ORDER BY, GROUP BY,    *
  *                      or set function DISTINCT when hybrid    *
  *                      join is chosen with SORTN_JOIN=N, an    *
  *                      index matches the ORDER BY, GROUP BY,   *
  *                      or set function DISTINCT columns, and   *
  *                      no extra sort is added to handle this   *
  *                      sorting.                                *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Incorrect output may occur for a query containing ORDER BY,
  GROUP BY, or set function DISTINCT when hybrid join is chosen
  with SORTN_JOIN=N, an index matches the ORDER BY, GROUP BY, or
  set function DISTINCT columns, and no extra sort is added
  to handle this sorting.
  
  The chosen access path included a RID list scan which did
  not preserve the order provided by the index.
  
  Additional Keywords:
  INCORROUT SQLINCORROUT SQLINCORR DB2INCORR/K SQLORDERBY
  SQLGROUPBY SQLDISTINCT SQLHYBRID SQLHYBRIDJOIN HYBRIDJOIN
  

Problem conclusion

• Code is added to include the extra sort in the situation
  described above.  If the estimated cost of the new access path
  with the extra sort is higher than a different access path, an
  access path without hybrid join may be chosen.  An access
  path with an extra sort may be chosen if it is determined that
  the sort is needed to prevent incorrect output.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UK93437 UK93438

Modules/Macros

• DSNXOTS1
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK93437

     UP13/04/30 P F304

• R910 PSY UK93438

     UP13/04/30 P F304

Fix is available

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