Drop a column from a Range Partitioned and Compressed table - oracle

Question

I have a table with data and need to remove a column, which is marked as unused. But it gives the error due to the compressed table.
I have used the command
ALTER TABLE <table name> MOVE NOCOMPRESS NOLOGGING PARALLEL 4;
But it gives this error:
ORA-14511: cannot perform operation on a partitioned object
How can I disable the partitioned? And how can I remove the unused column?

Answer 1

No, you cannot move partitioned table with one alter table statement, you need to perform relocation of that table into a new segment partition by partition:
Create test table:
SQL> create table t1(
2 col1 number,
3 col2 number
4 )
5 partition by range(col1) (
6 partition p_1 values less than (10) compress,
7 partition p_2 values less than (20) compress
8 );
Table created.
Populate test table with some sample data:
SQL> insert into t1(col1, col2)
2 select level
3 , level
4 from dual
5 connect by level <= 3;
3 rows created.
SQL> commit;
Commit complete.
SQL> select * from t1;
COL1 COL2
---------- ----------
1 1
2 2
3 3
Drop column statement fails:
SQL> alter table t1 drop column col2;
alter table t1 drop column col2
*
ERROR at line 1:
ORA-39726: unsupported add/drop column operation on compressed tables
Table relocation fails:
SQL> alter table t1 move nocompress;
alter table t1 move nocompress
*
ERROR at line 1:
ORA-14511: cannot perform operation on a partitioned object
Perform relocation of each partition:
SQL> alter table t1 move partition p_1 nocompress;
Table altered.
SQL> alter table t1 move partition p_2 nocompress;
Table altered.
When there are too many partitions, you can easily generate alter table statements while querying user_tab_partitions data dictionary view. For example:
SQL> column res format a50
SQL> select 'alter table ' || t.table_name ||
2 ' move partition ' || t.partition_name ||
3 ' nocompress;' as res
4 from user_tab_partitions t
5 where t.table_name = 'T1';
RES
--------------------------------------------------
alter table T1 move partition P_1 nocompress;
alter table T1 move partition P_2 nocompress;
After you have moved all partitions with nocompress option, you can drop column(s) issuing:
alter table t1 drop column col2
statement, or
alter table t1 drop unused columns
statement, if you already marked column(s) as unused before relocation.
Dropping unused columns:
Make col2 unused
SQL> alter table t1 set unused(col2);
Table altered.
List tables with unused columns in our schema
SQL> column table_name format a5
SQL> column table_name format a5
SQL> select *
2 from user_unused_col_tabs;
TABLE COUNT
----- ----------
T1 1
Relocate partitions
SQL> alter table T1 move partition P_1 nocompress;
Table altered.
SQL> alter table T1 move partition P_2 nocompress;
Table altered.
Drop unused columns:
SQL> alter table t1 drop unused columns;
Table altered.
Make sure we dropped everything we wanted to drop. Col2 is gone:
SQL> desc t1;
Name Null? Type
-------- -------- -----------
COL1 NUMBER
There are no tables with unused columns:
SQL> select *
2 from user_unused_col_tabs;
no rows selected