Question

I have some trouble when trying to update a table by looping cursor which select from source table through dblink.

I have two database DB1, DB2.

They are two different database instance.
And I am using this following statement in DB1:

CURSOR TestCursor IS
    SELECT  a.*, 'A' TEST_COL_A, 'B' TEST_COL_B
    FROM rpt.SOURCE@DB2  a;
BEGIN
    For C1 in TestCursor loop
        INSERT into  RPT.TARGET 
        (

           /*The company_name and cust_id are select from SOURCE table from DB2*/  
           COMPANY_NAME, CUST_ID, TEST_COL_A, TEST_COL_B

        ) 
        values
        (  
           C1.COMPANY_NAME, C1.CUST_ID, C1.TEST_COL_A , C1.TEST_COL_B
        ) ;

    End loop;

    /*Some code...*/

End

Everything works fine until I add a column “NEW_COL” to SOURCE table@DB2

The insert data got the wrong value.

The value of TEST_COL_A , as I expect, should be ‘A’.

However, it contains the value of NEW_COL which i add at SOURCE table.

And the value of TEST_COL_B contains ‘A’.

Have anyone encounter the same issue?
It seems like oracle cache the table columns when it compile.
Is there any way to add a column to source table without recompile?

Answer 1

According to this:

Oracle Database does not manage
dependencies among remote schema
objects other than
local-procedure-to-remote-procedure
dependencies.

For example, assume that a local view
is created and defined by a query that
references a remote table. Also assume
that a local procedure includes a SQL
statement that references the same
remote table. Later, the definition of
the table is altered.

Therefore, the local view and
procedure are never invalidated, even
if the view or procedure is used after
the table is altered, and even if the
view or procedure now returns errors
when used. In this case, the view or
procedure must be altered manually so
that errors are not returned. In such
cases, lack of dependency management
is preferable to unnecessary
recompilations of dependent objects.

In this case you aren’t quite seeing errors, but the cause is the same. You also wouldn’t have a problem if you used explicit column names instead of *, which is usually safer anyway. If you’re using * you can’t avoid recompiling (unless, I suppose, the * is the last item in the select list, in which case any extra columns on the end wouldn’t cause a problem – as long as their names didn’t clash).