IT28782: ALTER TABLE DROP CONSTRAINT DOES NOT INVALIDATE THE DEPENDENT PACKAGE AND CAUSES WRONG RESULTS TO BE RETURNED

APAR status

• Closed as program error.

Error description

• When there is a constraint defined on a table and a query makes
  use of the constraint for data partition elimination, a
  dependency
  on the constraint should be recorded for the query package.  Db2
  failed to record the dependency.  The result is that a row
  inserted
  after dropping the constraint, that would have violated this
  constraint,
  may not be returned by the query.  For example:
  
      CREATE TABLE T ( C1 INT NOT NULL, C2 INT NOT NULL )
               PARTITION BY RANGE(C2)
               (PART "P01" STARTING(1) ENDING(10),
                PART "P02" STARTING(11) ENDING(20) );
  
      CREATE INDEX I ON T ( C2 ASC, C1 ASC) PARTITIONED;
  
      ALTER TABLE T
        ADD CONSTRAINT C CHECK (C2 BETWEEN 1 AND 10)
        ENFORCED ENABLE QUERY OPTIMIZATION;
  
      -- Returns 0 rows as expected since table is empty.  Query
      -- package is stored in the dynamic package cache
      SELECT * FROM T WHERE C1 = 99;
  
      C1          C2
      ----------- -----------
        0 record(s) selected.
  
      -- Drop constraint, this should invalidate dynamic package
      ALTER TABLE T DROP CONSTRAINT C;
  
      -- Insert value outside of dropped constraint;
      INSERT INTO T VALUES ( 99, 11);
  
      -- Same query as before, now it should return the newly
      -- inserted row, but does not because Db2 failed to
      -- record dependency on the constraint
      SELECT * FROM T WHERE C1 = 99;
  
      C1          C2
      ----------- -----------
        0 record(s) selected.
  

Local fix

• For static queries (e.g. embedded C or SQL procedures), manually
  rebind the corresponding package(s).  For dynamic queries,
  either flush the dynamic package cache (FLUSH PACKAGE CACHE
  DYNAMIC), or close and re-establish database connection.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * ALL                                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to Db2 11.1 Mod 4 Fixpack 5 or higher                *
  ****************************************************************
  

Problem conclusion

• First fixed in Db2 11.1 Mod 4 Fixpack 5
  

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

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels

• RB10 PSN

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