IC98349: A QUERY WITH AN OR PREDICATE MIGHT RETURN INCORRECT RESULTS

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

• A query might return incorrect results when the query has the
  following pattern:
  1. The query contains a subquery block, called subQ1, that
  references a base table BT1, called that quantifier Q1, and
  another subquery, called subQ2
  2. The subQ2 block references the same base table BT1. Call that
  quantifier Q2.
  3. The subQ2 block has an OR predicate, called orPrd, qualifying
  all the following conditions:
  3.a. The orPrd predicate takes the form (orPrd1 OR orPrd2 [OR
  ...]).  One example could be an orPD predicate with at least two
  OR subterms denoted as orPrd1 and orPrd2.
  3.b. The orPrd predicate references column colX from Q1, and
  orPrd2 references column colX from Q2. In other words, orPrd1 is
  a correlation predicate, orPrd2 is local predicate, and their
  referenced columns derive from the same base table column.
  3.c. The orPrd1 and orPrd2 predicates are exactly matched or
  subsume each other. For example, Q1.colX=1 and Q2.colX = 1 are
  exactly matched, Q1.colX in (1,2) is subsumed by Q2.colX in
  (1,2,3).
  4. The query is compiled at optimization level 5 or above.
  
  The symptom is in the optimized statement when after either the
  orPrd1 or orPrd2 predicates are removed.
  

Local fix

• Reduce the query optimization level to below 5.  For example,
  issue the "db2 set current query optimization 2" command to
  reduce optimization level to 2.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users                                                    *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to DB2 version 10.1.0.4.                             *
  ****************************************************************
  

Problem conclusion

• The problem is first fixed in DB2 version 10.1.0.4.
  

Temporary fix

Comments

APAR Information

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

  IC98331

• 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