Virtual column based partitioning

Question

Hi,
we have a non-partitioned table in a production database and wish to partition it based on an expression. Since we are on 11.2 the first thing that comes to mind is virtual column based partitioning. The "problem" is that in order to partition by a virtual column, you have to create one, and adding a new column to a table could break any application that doesn't reference the existing columns by name, e.g. "SELECT *" or. "INSERT INTO table VALUES(....)".
My question is: is it possible to somehow specify the expression on which to partition directly in the "partition by" clause rather than specifying it as a virtual column definition?
Example:
Instead of this..
SQL> create table test (
  2    id             number not null,
  3    content        varchar2(10),
  4    record_type    varchar2(1) generated always as (case when (substr(content, 1, 1)='B' and not substr(content, 1, 3)='Bxy') then 'B' else 'A' end) virtual
  5  )
  6  partition by list(record_type)
  7  (
  8    partition partA values ('A'),
  9    partition partB values ('B')
10  );
Table created...I'd like to use something like this:
SQL> create table test (
  2    id             number not null,
  3    content        varchar2(10)
  4  )
  5  partition by list((case when (substr(content, 1, 1)='B' and not substr(content, 1, 3)='Bxy') then 'B' else 'A' end))
  6  (
  7    partition partA values ('A'),
  8    partition partB values ('B')
  9  );
partition by list((case when (substr(content, 1, 1)='B' and not substr(content, 1, 3)='Bxy') then 'B' else 'A' end))
ERROR at line 5:
ORA-00904: : invalid identifierThank you in advance for any answers.
Regards,
Jure

Answer 1

adding a new column to a table could break any application that doesn't reference the existing columns by name, e.g. "SELECT *" or. "INSERT INTO table VALUES(....)". "Ok, i got it. You mean, in application you are using select * from yourtable; and those data is being used by a datagrid or any control, then where that application will show / handle the new column data right ?
Yes, thats why DBA and developers do SDLC (Software Development Life Cycle); that our table will be looks like this, these will be columns, these will be their data types, these will be followed in naming convention, privileges, indexes, storage parameters, constraints, dependent objects etc. Now after creating the table, you found a need to add a column, it means there was some lapses happened at the design time/phase or business requirements are newly defined.
So, as far as concerned of select * ... ; you have to change in the application by :
select col1, col2, new_col from your table... (as per order of your datagrid control columns). There is no other solution, you have to change in application code at every place where you have used select * and if those statements are being merged / deals into a control)
New column addition will hamper only at select * from... not with any INSERT/UPDATE/DELETE, because if they are running fine it means, they have well written column references. For DMLs you need not worry so far.
By the way, what is your technology for application ? I have worked on couple of applications in ASP.NET with using datagrid which auto add/removes the columns in itself as per cursor result (not rememberring the exact property of it though)
Regards
Girish Sharma