IC71194: UPDATE QUERY WITH 'WHERE EXISTS' RUNS SLOWER IN 11.50 THAN IN 9.40

APAR status

• Closed as program error.

Error description

• Update query with 'where exists' in 9.40.FC7 or lower generates
  a different query plan than the query plan in 11.50 and runs 10
  times faster in 9.40.FC7 or lower.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users of 9.40.xC8 or later, 10.00.xC4 or later, all 11.10    *
  * and 11.50 users.                                             *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * A query involving multiple subqueries may have sub-optimal   *
  * query plans under the following conditions:                  *
  *  - the main query involves a large table                     *
  *  - one of the subqueries involves only small tables, and     *
  * only equi-join predicates between main query tables and      *
  * subquery tables                                              *
  *  - one of the subqueries has non-equal join predicates       *
  * between main query tables and subquery tables                *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to 11.50.xC8.                                        *
  ****************************************************************
  

Problem conclusion

• The problem is fixed in 11.50.xC8.
  

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:

Fix information

• Fixed component name

  IBM IDS ENTRP E

• Fixed component ID

  5724L2304

Applicable component levels

• RB15 PSN

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