IC99818: SQL STATEMENT WITH UNCORRELATED SUBQUERY PREDICATE MIGHT RETURN INCORRECT RESULTS WHEN INTRA_PARALLEL IS ENABLED

DB2 Version 10.1 Fix Pack 4 for Linux, UNIX, and Windows
DB2 Version 10.1 Fix Pack 6 for Linux, UNIX, and Windows

APAR status

• Closed as program error.

Error description

• An SQL statement that satisfies the following conditions might
  return an incorrect result set containing values that do not
  qualify the clauses in the WHERE clause when INTRA_PARALLEL is
  enabled:
  - the statement contains an uncorrelated subquery predicate
  nested within an uncorrelated EXISTS subquery predicate
  - the query optimizer converts the EXISTS subquery to a join
  - the access plan generated by the optimizer is parallelized
  
  The following is an example of a statement that satisfies the
  above conditions
  
  SELECT DISTINCT A1 FROM T1
  WHERE EXISTS (SELECT A2 FROM T2 WHERE B2 <> ALL (SELECT B3 FROM
  T3 WHERE A3 BETWEEN 1 and 10);
  

Local fix

• Disable INTRA_PARALLEL for the problematic statement by setting
  the CURRENT DEGREE special register to 1.
  

Problem summary

• Users Affected: All users
  Problem Description: see error description
  

Problem conclusion

• Problem is first fixed in DB2 UDB version
  10.1 fix pack 4
  

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:

  IT01084 IT01085 IT01086 IT01095

Fix information

• Fixed component name

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels

• RA10 PSN

     UP