IT20786: INCORRECT RESULT POSSIBLE WHEN CASE AND ANOTHER PREDICATE HAVE THE SAME COMPARISON OPERATION

Db2 Version 11.1 Mod2 Fix Pack2 iFix001 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod2 Fix Pack2 iFix002 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod 3 Fix Pack 3 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod3 Fix Pack3 iFix001 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod3 Fix Pack3 iFix002 for Linux, UNIX, and Windows

APAR status

• Closed as program error.

Error description

• If SQL against COLUMNAR table has 2 predicates , one of them
  CASE and part of the CASE or entire CASE condition matches the
  other predicate, then we could eliminate the second predicate by
  mistake.
  
  Example:
  
  SELECT * FROM T WHERE ( SUBSTR(A,1,1) = 'B' ) AND CASE WHEN (
  SUBSTR(A,1,1) = 'B' ) THEN B ELSE B END <> 0
  
  ( SUBSTR(A,1,1) = 'B' ) is used as it's own predicate AND as
  condition in CASE statement.
  
  In some cases we could lose this predicate and only apply CASE
  WHEN ( SUBSTR(A,1,1) = 'B' ) THEN B ELSE B END <> 0 which will
  return extra rows.
  

Local fix

• rewrite query to avoid this situation or install this fix.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
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  * PROBLEM DESCRIPTION:                                         *
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  * RECOMMENDATION:                                              *
  * Upgrade to Db2 11.1 Mod 2 Fix Pack 2 iFix001 or higher       *
  ****************************************************************
  

Problem conclusion

• First fixed in Db2 11.1 Mod 2 Fix Pack 2 iFix001
  

Temporary fix

Comments

APAR Information

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

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

  IT20790

Fix information

• Fixed component name

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels

• RB10 PSN

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