IC68045: SELECT WITH SUBQUERY ON VIEW WITH UNION IS SLOW WHEN EXECUTED FROM PROCEDURE

APAR status

• Closed as program error.

Error description

• A SELECT with subquery on a view with UNION is slow when it is
  executed from a procedure.
  
  Executing the SELECT outside of the procedure shows that the
  subquery is applied as an index filter on the tables in the
  view.
  
  Executing the SELECT from a procedure shows that the view is
  materialized again for the main query and the subquery is
  applied to the temp table for the view.
  
  
  Example:
  
  create view myview (id,c1,c2,c3,c4)
  as
  select id,c1,c2,c3,c4 from tab1
  union all
  select id,c1,c2,c3,c4 from tab2
  union all
  select id,c1,c2,c3,c4 from tab3;
  
  select c4
  from myview
  where id in (select max(id)
               from myview
               where
               id=40 );
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users having union all view and subquery in SPL              *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * When union all view is used on SPL along with subquery, IDS  *
  * does not use available index filters inside subquery. Since  *
  * sequential scan is used, IDS gives performance issues in SPL *
  * as compared to stand alone query.                            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to 11.50.xC8.                                        *
  ****************************************************************
  

Problem conclusion

• 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

     UP