Disable Automatic Optimizer Statistics

Question

Hi there
I wanted to query user_tab_modifications to track, number of rows updated in a week. Since this view is refreshed automatically when Automatic Optimizer Statistics gathers statistics, i disabled the Automatic Optimizer Statistics. Now i am executing execute dbms_stats.FLUSH_DATABASE_MONITORING_INFO(); manually to get the view populated with number of rows updated.
My concern here is , will i get the exact number of rows updated in a week from user_tab_modifications by doing this ? Also, is there anything else that is also updating this view apart from optimizer statistics that are gathered on a table.
Thanks

Answer 1

You could try writing some PLSQL on your own.
How about :
SQL> create table count_X_updates (update_count number);
Table created.
SQL> insert into count_X_updates values (0);
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> create table X (col_1 varchar2(5), col_2 varchar2(5), col_3 number);
Table created.
SQL> insert into X values ('a','first',1);
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> create or replace trigger count_x_updates_trg
  2  after update of col_1,col_2,col_3
  3  on X
  4  for each row
  5  declare prev_cnt number;
  6  begin
  7  update count_X_updates set update_count = update_count+1;
  8* end;
SQL> /
Trigger created.
SQL>  update x set col_1 = 'b', col_2='secnd',col_3=2;
1 row updated.
SQL> commit;
Commit complete.
SQL> select * from count_X_updates;
UPDATE_COUNT
           1
SQL>  update x set col_1 = 'c' where col_3=2;
1 row updated.
SQL> commit;
Commit complete.
SQL> select * from count_X_updates;
UPDATE_COUNT
           2
SQL> select * from x;
COL_1 COL_2      COL_3
c     secnd          2
SQL>Note : This trigger code has to be improved because
a. Multiple sessions might get the same value
b. It introduces a point of serialisation -- multiple session will wait on a row lock on the table count_X_updates -- effectively meaning that all other sessions attempting to update X will wait (even if they are updating different rows in X) till each preceding one issues a COMMIT.
So, this demo code is only to show you PLSQL Triggers. But it cannot be used in Production.
Practice some PLSQL. Read up on autonomous transactions.
Hemant K Chitale