# How to alter an existing partitioned table to add sub-partitions to it

oracleoracle-12cpartitioning

This forum has helped me earlier on many occasions and now I need someone to help me with this.

I am looking to convert a pre-existing partitioned (range) table – to sub-partitioned (composite range-list).

1) I Range Partitioned an existing table using the query below:

alter table PART_TEST
modify PARTITION BY RANGE (CREATEDATE)
(
PARTITION p1 VALUES LESS THAN (TO_DATE('15-MAY-2019', 'DD-MON-YYYY')),
PARTITION p2 VALUES LESS THAN (TO_DATE('16-MAY-2019', 'DD-MON-YYYY')),
PARTITION p3 VALUES LESS THAN (maxvalue)) online;


2) Then I tried to alter the table to add sub-partitions (list) using the query below:

ALTER TABLE PART_TEST
MODIFY PARTITION P1
VALUES ('1') tablespace TEST_PART;


But I see this error:

Error report – ORA-14253: table is not partitioned by composite
partition method
14253. 00000 – "table is not partitioned by Composite Range method"
*Cause: The table in a subpartition maintenance operation (ALTER TABLE
EXCHANGE/MODIFY/MOVE/TRUNCATE SUBPARTITION, or ALTER TABLE MODIFY
PARTITION ADD/COALESCE SUBPARTITION command must be partitioned
by Composite Range method
*Action: Ensure that the table is partitioned by Composite Range method

Below is what I am tasked with,

Scenario – 1:
==> I want to have my existing partitions(range) subpartitioned (list) so that my old data is usable. The data in each of my partitions have to be moved to a sub-partition,

Scenario – 2: Then revert back to partition level (reverse migrate),
==> I mean the data from all of the sub-partitions within each partition is moved to be at the partition level and no sub-partitions are left in the database.

Is it possible and is there a way to do so?
If so how to implement the above scenarios – convert existing partitions(range) to sub-partitioned (Range-list) – and how to move back the data from sub-partitions to each of its partition back and no-sub partitions are left.

# Scenario 1 - redefine the table

Your SQL is adding a sub-partition, not redefining the table. I suspect you need to redefine the table to have sub-partitions before you can add a sub-partition.

12.2c+

The ability to change a non-partitioned table into a partitioned table via ALTER TABLE was introduced in 12.2c.

Looking at the documentation, it appears that you can change a RANGE partitioned table into a RANGE-LIST partition in the same way. I haven't tried; be cautious; use DEV for practice.

pre-12.2c

DBMS_REDEFINITION is the de facto way of changing a table between non-partitioned and partition designs.

Any way, I suspect that the only way to do this is with DBMS_REDEFINITION.