IC72113: OPTIMIZER CHOOSES INAPPROPRIATE KEY-FIRST SCAN WHEN JOIN INCLUDES SMALL TEMP TABLE ON A VERY SIMPLE SELECT STATEMENT

APAR status

• Closed as program error.

Error description

• When joining a small temp table with a regular table, the
  optimizer chooses a key-first scan which is more costly
  resulting in a much longer run time.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All 11.50 users.                                             *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * When a query joins a table with explicit "rowid" reference,  *
  * such as tab1.col = tab2.rowid, the optimizer may choose      *
  * sub-optimal query plan.                                      *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to 11.50.xC9.                                        *
  ****************************************************************
  

Problem conclusion

• The problem is fixed in 11.50.xC9.
  

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

     UP