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понедельник, 30 января 2017 г.

DBMS_METADATA.GET_SXML_DDL may produce incorrect DDL for trigger in EBR environment

I have recently discovered a case when DBMS_METADATA.GET_SXML_DDL returns incorrect DDL for the trigger in an EBR environment.
Here is a test case to reproduce the issue that is present in 12.1.0.2.170117 and 11.2.0.4.161018:
SQL> grant connect, create table, create view, create trigger to tc identified by tc;

Grant succeeded.

SQL> 
SQL> alter user tc enable editions for view,trigger;

User altered.

SQL> 
SQL> conn tc/tc
Connected.
SQL> 
SQL> create table t (
  2    x int)
  3  /

Table created.

SQL> 
SQL> create or replace editioning view ev
  2  as
  3  select *
  4    from t
  5  /

View created.

SQL> 
SQL> create or replace trigger trg
  2  before update of x on ev
  3  declare
  4  begin
  5    null;
  6  end;
  7  /

Trigger created.
Let us look at the DDL of the trigger returning by DBMS_METADATA.GET_DDL and DBMS_METADATA.GET_SXML_DDL functions.
SQL> select dbms_metadata.get_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------

  CREATE OR REPLACE EDITIONABLE TRIGGER "TC"."TRG"
before update of x on ev
declare
begin
  null;
end;
ALTER TRIGGER "TC"."TRG" ENABLE


SQL> select dbms_metadata.get_sxml_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_SXML_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------
  CREATE OR REPLACE TRIGGER "TC"."TRG"
  BEFORE UPDATE OF X ON "TC"."EV"
  declare
begin
  null;
end;
They are pretty much the same. Now I change the status of my trigger. Please note the highlighted lines showing the differences:
SQL> alter trigger trg enable;

Trigger altered.

SQL> 
SQL> select dbms_metadata.get_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------

  CREATE OR REPLACE EDITIONABLE TRIGGER "TC"."TRG"
before update of x on ev
declare
begin
  null;
end;
ALTER TRIGGER "TC"."TRG" ENABLE


SQL> select dbms_metadata.get_sxml_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_SXML_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------
  CREATE OR REPLACE TRIGGER "TC"."TRG"
  BEFORE UPDATE OF X, X ON "TC"."EV"
  declare
begin
  null;
end;
I have ended up with two X columns in the output of DBMS_METADATA.GET_SXML_DDL, which is, in fact, a non-working DDL statement.
I played more with this issue and I have eventually obtained four X columns and it is not a limit:
SQL> alter trigger trg disable;

Trigger altered.

SQL> 
SQL> select dbms_metadata.get_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------

  CREATE OR REPLACE EDITIONABLE TRIGGER "TC"."TRG"
before update of x on ev
declare
begin
  null;
end;
ALTER TRIGGER "TC"."TRG" DISABLE


SQL> select dbms_metadata.get_sxml_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_SXML_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------
  CREATE OR REPLACE TRIGGER "TC"."TRG"
  BEFORE UPDATE OF X, X, X ON "TC"."EV"
  declare
begin
  null;
end;
  ALTER TRIGGER "TC"."TRG" DISABLE


SQL> 
SQL> alter trigger trg enable;

Trigger altered.

SQL> 
SQL> select dbms_metadata.get_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------

  CREATE OR REPLACE EDITIONABLE TRIGGER "TC"."TRG"
before update of x on ev
declare
begin
  null;
end;
ALTER TRIGGER "TC"."TRG" ENABLE


SQL> select dbms_metadata.get_sxml_ddl( 'TRIGGER', 'TRG') from dual;

DBMS_METADATA.GET_SXML_DDL('TRIGGER','TRG')
--------------------------------------------------------------------------------
  CREATE OR REPLACE TRIGGER "TC"."TRG"
  BEFORE UPDATE OF X, X, X, X ON "TC"."EV"
  declare
begin
  null;
end;
The DBMS_METADATA.GET_SXML_DDL procedure uses a SELECT statement similar to the above to obtain the DDL:
SELECT /*+all_rows*/ 
       SYS_XMLGEN(
         VALUE(KU$), 
         XMLFORMAT.createFormat2('TRIGGER_T', '7')), 
       KU$.OBJ_NUM 
  FROM SYS.KU$_TRIGGER_VIEW KU$ 
 WHERE NOT (KU$.BASE_OBJ IS NOT NULL AND BITAND(KU$.BASE_OBJ.FLAGS,128)!=0) 
   AND KU$.SCHEMA_OBJ.NAME = 'TRG' 
   AND KU$.SCHEMA_OBJ.OWNER_NAME = 'TC';
The column list for the trigger comes from this part of the SYS.KU$_TRIGGER_VIEW view:
          cast(multiset(select * from ku$_triggercol_view tv
                        where tv.obj_num=t.obj#
                      ) as ku$_triggercol_list_t
             ),
The code of the KU$_TRIGGERCOL_VIEW view is:
CREATE OR REPLACE FORCE NONEDITIONABLE VIEW "SYS"."KU$_TRIGGERCOL_VIEW" OF "SYS"."KU$_TRIGGERCOL_T"
  WITH OBJECT IDENTIFIER (obj_num,intcol_num,type_num) AS
  select '1','0',
         tc.obj#, tc.col#, tc.type#, tc.position#, tc.intcol#, c.name,
         (select a.name from attrcol$ a where
                        a.obj#=tc.obj# and a.intcol#=tc.intcol#)
  from col$ c, triggercol$ tc, trigger$ t
  where tc.obj#=t.obj#
    and c.obj#=t.baseobject
    and c.intcol#=tc.intcol#
And the final part of the puzzle is the TRIGGERCOL$ table:
SQL> select * from sys.triggercol$ where obj#=(select object_id from dba_objects where owner='TC' and object_name='TRG');

      OBJ#       COL#      TYPE#  POSITION#    INTCOL#
---------- ---------- ---------- ---------- ----------
    214352          1          0          0          1
    214352          1          0          0          1
    214352          1          0          0          1
    214352          1          0          0          1
    214352          1       1024          0          1
It gets one row each time I execute the "ALTER TRIGGER ENABLE/DISABLE" statement. I think Oracle Developers should filter the rows because there is only one row with TYPE#=1024.
DBMS_METADATA.GET_DDL returns correct DDL and it seems to be come from the DDL passed by a user.
Conversely, DBMS_METADATA.GET_SXML_DDL tries to reconstruct the user's DDL and it messes things up.

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