Best way to update/insert into a table based on a remote table.

Question

I have two very large enterprise tables in an Oracle 10g database. One table keeps the historical information of the other table. The problem is, I'm getting to the point where the records are just too many that my insert update is taking too long and my session is getting killed by the governor.

Here's a pseudocode of my update process:

sqlsel := 'SELECT col1, col2, col3, col4 sysdate  
        FROM table2@remote_location dpi
         WHERE (col1, col2, col3) IN
               (
                SELECT col1, col2, col3
                  FROM table2@remote_location 
                 MINUS
                SELECT DISTINCT col1, col2, col3
                  FROM table1 mpc
                 WHERE facility = '''||load_facility||'''
               )';

EXECUTE IMMEDIATE sqlsel BULK COLLECT
                 INTO table1;

I've tried the MERGE statement:

MERGE INTO table1 t1
USING (
  SELECT col1, col2, col3  FROM table2@remote_location 
  ) t2
ON (
t1.col1 = t2.col1 AND
t1.col2 = t2.col2 AND
t1.col3 = t2.col3 
)

WHEN NOT MATCHED THEN
  INSERT (t1.col1, t1.col2, t1.col3, t1.update_dttm  )
  VALUES (t2.col1, t2.col2, t2.col3, sysdate  )

But there seems to be a confirmed bug on versions prior to Oracle 10.2.0.4 on the merge statement when doing a merge using a remote database. The chance of getting an enterprise upgrade is slim so is there a way to further optimize my first query or write it in another way to have it run best performance wise?

Thanks.

Answer 1

Have you looked at Materialized Views to perform your sync? A pretty good into can be found at Ask Anantha. This Oracle white paper is good, too.

Answer 2

If there are duplicate col1/col2/col3 entries in table2@remote, then your query will return them. if they are not needed, then you could do a

SELECT col1, col2, col3, sysdate  
FROM (
     SELECT col1, col2, col3
     FROM table2@remote_location 
     MINUS
     SELECT col1, col2, col3
     FROM table1 mpc
     WHERE facility = '''||load_facility||'''
     )

You can get rid of the DISTINCT too. MINUS is a set operation and so it is unnecessary.