Tuesday, June 19, 2012

Online Redefinition and Reference Partitioning

Reference partitioning combined with dbms_redefinition can result in a perpetually disabled foreign key constraint (I'm using 11.2.0.3 as an example):
SQL> create table p (
  2   n number primary key
  3  ) partition by list (n)
  4  (
  5   partition p1 values (1)
  6  );
 
Table created
 
SQL> create table r1 (n number not null);
 
Table created
 
SQL> create table r2 (
  2   n number not null,
  3   constraint fk_r$n foreign key (n) referencing p (n)
  4  ) partition by reference (fk_r$n);
 
Table created
 
SQL> exec dbms_redefinition.start_redef_table(user, 'R1', 'R2', options_flag => dbms_redefinition.cons_use_rowid);
 
PL/SQL procedure successfully completed
 
SQL> exec dbms_redefinition.finish_redef_table(user, 'R1', 'R2');
 
PL/SQL procedure successfully completed
 
SQL> select status, validated from user_constraints where constraint_name='FK_R$N';
 
STATUS   VALIDATED
-------- -------------
DISABLED NOT VALIDATED
The annoying part comes when you realize that you can't do anything about it (at least not by normal means):
SQL> alter table r1 enable constraint FK_R$N;
 
alter table r1 enable constraint FK_R$N
 
ORA-14650: operation not supported for reference-partitioned tables
 
SQL> alter table r1 enable novalidate constraint FK_R$N;
 
alter table r1 enable novalidate constraint FK_R$N
 
ORA-14650: operation not supported for reference-partitioned tables
Surprisingly enough the constraint actually works as far as reference partitioning is concerned. However, it results in an "unclean" status which can't be fixed! Of course the view just shows us what we have in cdef$:
SQL> select con#, enabled, defer
  2   from sys.cdef$
  3   where con# =
  4   (select con#
  5    from sys.con$
  6    where owner#=(select user# from sys.user$ where name=user)
  7     and name= 'FK_R$N'
  8   );
 
      CON#    ENABLED      DEFER
---------- ---------- ----------
     10997                   512
ENABLED set to NULL will decode to DISABLED while the following results in NOT VALIDATED:
SQL> select decode(bitand(512, 4), 4, 'VALIDATED', 'NOT VALIDATED') VALIDATED from dual;
 
VALIDATED
-------------
NOT VALIDATED
So what we really need is ENABLED set to 1 and DEFER set to 516. Of course, playing with the data dictionary in such a way is a big no-no on production system without blessing of Oracle support, but since I'm on my sandbox database I'll give it a shot:
SQL> update cdef$ set enabled=1, defer=516 where con#=10997;

1 row updated.

SQL> commit;

Commit complete.

SQL> startup force
ORACLE instance started.

Total System Global Area  400846848 bytes
Fixed Size                  2228784 bytes
Variable Size             146804176 bytes
Database Buffers          243269632 bytes
Redo Buffers                8544256 bytes
Database mounted.
Database opened.

SQL> select status, validated from user_constraints where constraint_name='FK_R$N';
 
STATUS   VALIDATED
-------- -------------
ENABLED  VALIDATED
Looks like it worked :) Note that there is practically no way for a reference partitioning constraint to be either disabled or not validated -- the rows have to go somewhere, after all, so we don't introduce any logical inconsistencies by setting cdef$ values to what they really should be.

Footnote:
The bug number for this one is 13572659.

1 comment:

  1. Anonymous4:05 PM

    There is another related issue:

    Bug 13526773 Constraint becomes NOT VALIDATED after table is redefined by DBMS_REDEFINITION

    ReplyDelete