IT02563: NEW OPTIMIZER CHOICE FOR SUBSELECTS IN 12.10 CAN CAUSE MASSIVE PERFORMANCE ISSUES TO CERTAIN QUERIES

APAR status

• Closed as program error.

Error description

• 12.10 has a new plan shape that's not allowed in 11.50, where we
  put all the subquery tables first and do a duplicate removal
  before joining in all the main query tables.  Apparently in some
  cases the subquery tables are so large that the join among them
  is taking forever.
  
  There needs to be a fix so that this feature can be disabled, as
  it results in poor performance in some situations.
  

Local fix

• No fix available
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users of 12.10.xC1 through 12.10.xC4.                        *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Update to IDS-12.10.xC5                                      *
  ****************************************************************
  

Problem conclusion

• Problem Fixed In IDS-12.10.xC5
  

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

  INFORMIX SERVER

• Fixed component ID

  5725A3900

Applicable component levels

• RC10 PSN

     UP