IT13193: DB2 MIGHT PRODUCE INCORRECT RESULT WHEN EXECUTING QUERIES WITH INTERSECT AND DISTINCT

DB2 Version 10.1 Fix Pack 6 for Linux, UNIX, and Windows

APAR status

• Closed as program error.

Error description

• Under rare scenario, DB2 might produce incorrect results when
  the following conditions are true:
  1) The query contains an INTERSECT/INTERSECT ALL with 3 or more
  branches
  2) There is an explicit or implicit DISTINCT in the query
  3) One of the branches is guaranteed to produce one row
  
  eg.
  T1 (PK1 int not null primary key, FK1 int not null);
  T2 (PK2 int not null primary key, FK2 int not null);
  
  Select PK1 from T1 where PK1 = 1
  INTERSECT
  Select FK2 from T2 where PK2 in (1,2,3)
  INTERSECT
  Select PK1 from T1
  
  eg 2.
  Select DISTINCT col from
  (
    Select PK1 from T1 where PK1 = 1
    INTERSECT ALL
    Select FK2 from T2 where PK2 in (1,2,3)
    INTERSECT ALL
    Select PK1 from T1
  ) as INT(col);
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * ALL                                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to DB2 10.1 Fix Pack 6                               *
  ****************************************************************
  

Problem conclusion

• First fixed in DB2 10.1 Fix Pack 6
  

Temporary fix

Comments

APAR Information

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

  IT13020

• 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

• RA10 PSN UP

     FIX