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Oracle 19c introduces Hybrid Partitioning whereby you can have external and internal Partitions co-existing.  External Partitions are on storage (filesystem) outside the database.

Let's say we have a List Partitioned table for the widgets that we manufacture. The table is Partitioned by WIDGET_CLASS_ID, based on an ISO standard.  So all companies that manufacture widgets adopt the same WIDGET_CLASS_ID:

SQL> desc widgets_list
Name Null? Type
----------------------------------------- -------- ----------------------------
WIDGET_CLASS_ID VARCHAR2(5)
WIDGET_ID VARCHAR2(32)
WIDGET_NAME VARCHAR2(32)
WIDGET_DESCRIPTION VARCHAR2(128)

SQL>
SQL> l
1 select table_name, partitioning_type, partition_count
2 from user_part_tables
3* where table_name = 'WIDGETS_LIST'
SQL> /

TABLE_NAME PARTITION PARTITION_COUNT
-------------------------------- --------- ---------------
WIDGETS_LIST LIST 3

SQL>
SQL> l
1 select partition_name,high_value, num_rows
2 from user_tab_partitions
3* where table_name = 'WIDGETS_LIST'
SQL> /

PARTITION_NAME HIGH_VALUE NUM_ROWS
---------------- ---------------- ----------
P_A 'A' 1520
P_B 'B' 520
P_C 'C' 119

SQL>


Later, another widget manufacturer that manufactures widgets of CLASS_ID 'X' is acquired.  The WIDGETS_LIST table is in a non-Oracle database and is received as a CSV file.  We accept the CSV file onto a filesystem location :

sh-4.2$ pwd
/home/oracle/ACQUIRED_COMPANY
sh-4.2$ cat AC_Widgets_List.CSV
'X','ABCXX2','The1','cddfdaxx'
'X','XXD2','The2','dda3'
'X','XRC34','The3','ff33355312'
sh-4.2$


So, we have a CSV file "AC_Widgets_List.CSV" listing the widgets manufactured by this company. We want to add it to our WIDGETS_LIST table.

Enter user-name: / as sysdba

Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

SQL> alter session set container=ORCLPDB1;

Session altered.

SQL> create directory acquired_company as '/home/oracle/ACQUIRED_COMPANY';

Directory created.

SQL> grant read, write on directory acquired_company to hemant;

Grant succeeded.

SQL>
SQL> connect hemant/hemant@ORCLPDB1
Connected.
SQL>
SQL> l
1 alter table widgets_list
2 add external partition attributes (
3 type oracle_loader
4 default directory acquired_company
5 access parameters (
6 fields terminated by ','
7 (widget_class_id, widget_id, widget_name, widget_description)
8 )
9* )
SQL> /

Table altered.

SQL>
SQL> l
1 alter table widgets_list
2 add partition P_ACQ_CO values ('X')
3* external location ('AC_Widgets_List.CSV')
SQL> /

Table altered.

SQL>
SQL> exec dbms_stats.gather_table_stats('','WIDGETS_LIST');

PL/SQL procedure successfully completed.

SQL>
SQL> l
1 select partition_name, high_value, num_rows
2 from user_tab_partitions
3 where table_name = 'WIDGETS_LIST'
4* order by partition_position
SQL> /

PARTITION_NAME HIGH_VALUE NUM_ROWS
-------------------------------- ---------------- ----------
P_A 'A' 1520
P_B 'B' 520
P_C 'C' 119
P_ACQ_CO 'X' 3

SQL>
SQL> l
1* select * from widgets_list partition (P_ACQ_CO)
SQL> /

WIDGET_CLASS WIDGET_ID WIDGET_NAME
------------ -------------------------------- --------------------------------
WIDGET_DESCRIPTION
--------------------------------------------------------------------------------
'X' 'ABCXX2' 'The1'
'cddfdaxx'

'X' 'XXD2' 'The2'
'dda3'

'X' 'XRC34' 'The3'
'ff33355312'


SQL>


The rows in the "AC_Widgets_List.CSV" file are now visible as rows in a *Partition* in our Oracle Table WIDGETS_LIST.
Of course, these being external, cannot be modified by INSERT/UPDATE/DELETE DML.

The External Attribute Type that I used is ORACLE_LOADER to use the SQL Loader libraries on a filesystem file.  Oracle 19c also supports ORACLE_DATAPUMP, ORACLE_HDFS and ORACLE_HIVE to reference files stored in other types of storage.

Hybrid Partitions are supported with single-level Range and List partitioning methods.  ALTER TABLE to ADD, DROP and RENAME Partitions is supported.

An External Partition can be Exchanged with an External Non-Partitioned Table only.
.
.
UPDATE :  Later, if I update the CSV file (using an external editor) to remove the quotation mark :

sh-4.2$ cat AC_Widgets_List.CSV
X,ABCXX2,The1,cddfdaxx
X,XXD2,The2,dda3
X,XRC34,The3,ff33355312
sh-4.2$

SQL> l
1* select * from widgets_list partition (P_ACQ_CO)
SQL> /

WIDGET_CLASS_ID WIDGET_ID WIDGET_NAME
---------------- -------------------------------- --------------------------------
WIDGET_DESCRIPTION
------------------------------------------------------------------------------------
X ABCXX2 The1
cddfdaxx

X XXD2 The2
dda3

X XRC34 The3
ff33355312


SQL>


So, it is possible to edit the External Partition using other methods (here I used "vi" on Linux)
.
.
.
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Oracle 18c introduces the ability to convert a Partitioned Table from one Type to another -- e.g. from Hash Partitioning to Range Partitioning.  This is effectively a change of the Partitioning strategy for a table without actually having to manually rebuild the table.

I start with a Hash Partitioned Table.

SQL> create table customers(customer_id number, customer_name varchar2(200), customer_city_code number)
2 partition by hash (customer_id) partitions 4;

Table created.

SQL> select partitioning_type from user_part_tables
2 where table_name = 'CUSTOMERS'
3 /

PARTITION
---------
HASH

SQL> select partition_name from user_tab_partitions
2 where table_name = 'CUSTOMERS'
3 /

PARTITION_NAME
--------------------------------------------------------------------------------
SYS_P221
SYS_P222
SYS_P223
SYS_P224

SQL>
SQL> insert into customers
2 select dbms_random.value(1,1000001), dbms_random.string('X',25), mod(rownum,5)
3 from dual
4 connect by level < 1000001
5 /

1000000 rows created.

SQL> commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats('','CUSTOMERS');

PL/SQL procedure successfully completed.

SQL> select partition_name, num_rows
2 from user_tab_partitions
3 where table_name = 'CUSTOMERS'
4 /

PARTITION_NAME NUM_ROWS
---------------- ----------
SYS_P221 250090
SYS_P222 249563
SYS_P223 250018
SYS_P224 250329

SQL>


I now want to convert this Hash Partitioned Table to a Range Partitioned Table online.

SQL> alter table customers
2 modify
3 partition by range (customer_id)
4 (partition P_100K values less than (100001),
5 partition P_200K values less than (200001),
6 partition P_300K values less than (300001),
7 partition P_400K values less than (400001),
8 partition P_500K values less than (500001),
9 partition P_600K values less than (600001),
10 partition P_700K values less than (700001),
11 partition P_800K values less than (800001),
12 partition P_900K values less than (900001),
13 partition P_1MIL values less than (1000001),
14 partition P_2MIL values less than (2000001),
15 partition P_MAXVALUE values less than (MAXVALUE))
16 online;

Table altered.

SQL>
SQL> select partitioning_type
2 from user_part_tables
3 where table_name = 'CUSTOMERS'
4 /

PARTITION
---------
RANGE

SQL> exec dbms_stats.gather_table_stats('','CUSTOMERS');

PL/SQL procedure successfully completed.

SQL> col high_value format a12
SQL> select partition_name, high_value, num_rows
2 from user_tab_partitions
3 where table_name = 'CUSTOMERS'
4 order by partition_position
5 /

PARTITION_NAME HIGH_VALUE NUM_ROWS
---------------- ------------ ----------
P_100K 100001 100116
P_200K 200001 99604
P_300K 300001 99941
P_400K 400001 100048
P_500K 500001 99841
P_600K 600001 99920
P_700K 700001 100081
P_800K 800001 100024
P_900K 900001 100123
P_1MIL 1000001 100302
P_2MIL 2000001 0
P_MAXVALUE MAXVALUE 0

12 rows selected.

SQL>


The Hash Partitioned Table is now converted to a Range Partitioned Table.  The number of Partitions has been changed.  And the operation was performed online with the ONLINE keyword added to the ALTER TABLE ... statement.  The UPDATE INDEXES clauses can also be used to update existing Indexes on the Table.
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An excellent article that anyone promising, developing, maintaining or using any system that is non-trivial should read :

https://embeddedartistry.com/blog/2019/4/1/what-can-software-organizations-learn-from-the-boeing-737-max-saga
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Pre-12cRelease2, there were only three methods to convert a non-Partitioned Table to a Partitioned Table

(a) Create a new, empty, Partitioned Table and copy (using INSERT .... AS SELECT ... ) all the data from the non-Partitioned Table to the new, Partitioned Table (and subsequently rename the new Partitioned Table after renaming or dropping the old non-Partitioned Table)

(b) Create a new, empty, Partitioned Table and use EXCHANGE PARTITION to switch the non-Partitioned Table into the Partitioned Table (and then run subsequent SPLIT PARTITION or ADD PARTITION commands as needed to create the additional Partitions)

(c) Create an interim Partitioned Table and use DBMS_REDEFINITION to do an online copy of the data to the interim Partitioned Table and automatically switch the name at the end


12.2 introduced the ability to use ALTER TABLE  ... MODIFY PARTITION ... to convert a non-Partitioned Table to a Partitioned Table

I start with a non-Partitioned Table :

SQL> select table_name, partitioned
2 from user_tables
3 where table_name = 'SALES_DATA_NONPARTITIONED'
4 /

TABLE_NAME PAR
------------------------------ ---
SALES_DATA_NONPARTITIONED NO

SQL> select index_name, uniqueness, partitioned
2 from user_indexes
3 where table_name = 'SALES_DATA_NONPARTITIONED'
4 /

INDEX_NAME UNIQUENES PAR
------------------------------ --------- ---
SALES_DATA_UK UNIQUE NO

SQL>


I then convert it to a Range-Partitioned Table.

SQL> alter table sales_data_nonpartitioned
2 modify
3 partition by range (sale_date)
4 (
5 partition P_2015 values less than (to_date('01-JAN-2016','DD-MON-YYYY')),
6 partition P_2016 values less than (to_date('01-JAN-2017','DD-MON-YYYY')),
7 partition P_2017 values less than (to_date('01-JAN-2018','DD-MON-YYYY')),
8 partition P_2018 values less than (to_date('01-JAN-2019','DD-MON-YYYY')),
9 partition P_2019 values less than (to_date('01-JAN-2020','DD-MON-YYYY')),
10 partition p_MAXVALUE values less than (MAXVALUE)
11 )
12 online
13 update indexes
14 /

Table altered.

SQL>
SQL> alter table sales_data_nonpartitioned rename to sales_data;

Table altered.

SQL>
SQL> select partition_name, high_value
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4 order by partition_position
5 /

PARTITION_NAME HIGH_VALUE
---------------- --------------------------
P_2015 TO_DATE(' 2016-01-01 00:00
P_2016 TO_DATE(' 2017-01-01 00:00
P_2017 TO_DATE(' 2018-01-01 00:00
P_2018 TO_DATE(' 2019-01-01 00:00
P_2019 TO_DATE(' 2020-01-01 00:00
P_MAXVALUE MAXVALUE

6 rows selected.

SQL>
SQL> select index_name, partitioned, uniqueness, status
2 from user_indexes
3 where table_name = 'SALES_DATA'
4 /

INDEX_NAME PAR UNIQUENES STATUS
------------------------------ --- --------- --------
SALES_DATA_UK NO UNIQUE VALID

SQL>


The SALES_DATA_NONPARTITIONED was converted to a Range Partitioned Table.  If I didn't have to rename the table (e.g. if the table name was actually, properly SALES_DATA only), then there would be no need to lock the table as the RENAME command does.
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A TRUNCATE or DROP Partition makes Global Indexes on a Partitioned Table UNUSABLE.

You may be lucky if the target partition was empty, resulting in Oracle maintaining Global Indexes as valid.  However, the accepted rule is that you either (a) use the UPDATE INDEXES clause [resulting in the TRUNCATE or DROP taking longer to run, effectively locking the table partitions] OR  (b) do a REBUILD of the Indexes that become UNUSABLE after the TRUNCATE or DROP.

12c has introduced what it calls Asynchronous Global Index Maintenance.  With this feature present, the TRUNCATE or DROP runs much faster as a DDL without actually removing the target rows from the Global Indexes [but still requires the UPDATE INDEXES clause to be specified]

So, now in my 12.2 database I have these two Indexes on SALES_DATA :

SQL> select index_name, partitioned, status
2 from user_indexes
3 where table_name = 'SALES_DATA'
4 order by 2,1
5 /

INDEX_NAME PAR STATUS
------------------------------ --- --------
SALES_DATA_PK NO VALID
SALES_DATA_LCL_NDX_1 YES N/A

SQL>


I then TRUNCATE a non-empty Partition and check the Indexes

SQL> alter table sales_data truncate partition P_2015 update indexes;

Table truncated.

SQL>
SQL> select index_name, partitioned, status, orphaned_entries
2 from user_indexes
3 where table_name = 'SALES_DATA'
4 order by 2,1
5 /

INDEX_NAME PAR STATUS ORP
------------------------------ --- -------- ---
SALES_DATA_PK NO VALID YES
SALES_DATA_LCL_NDX_1 YES N/A NO

SQL>


The ORPHANED_ENTRIES column indicates that SALES_DATA_PK is subject to Asynchronous Index Maintenance.

This is the job that will do the Index Maintenance at 2am  :

SQL> l
1 select owner, job_name, last_start_date, next_run_Date
2 from dba_scheduler_jobs
3* where job_name = 'PMO_DEFERRED_GIDX_MAINT_JOB'
SQL> /

OWNER
---------------------------------------------------------------------------
JOB_NAME
---------------------------------------------------------------------------
LAST_START_DATE
---------------------------------------------------------------------------
NEXT_RUN_DATE
---------------------------------------------------------------------------
SYS
PMO_DEFERRED_GIDX_MAINT_JOB
20-MAR-19 10.18.51.215433 AM UTC
21-MAR-19 02.00.00.223589 AM UTC


SQL> !date
Wed Mar 20 20:05:24 SGT 2019

SQL>


So, I could
(1) wait for the next run of the job OR
(2) manually trigger the job (which will scan the entire database for all indexes that require such maintenance) OR
(3) Execute  DBMS_PART.CLEANUP_GIDX  to initiate the maintenance for the specific index OR
(4) Execute an ALTER INDEX REBUILD to make the Index USABLE again.

SQL> execute dbms_part.cleanup_gidx('HEMANT','SALES_DATA');

PL/SQL procedure successfully completed.

SQL> select index_name, partitioned, status, orphaned_entries
2 from user_indexes
3 where table_name = 'SALES_DATA'
4 order by 2,1
5 /

INDEX_NAME PAR STATUS ORP
------------------------------ --- -------- ---
SALES_DATA_PK NO VALID NO
SALES_DATA_LCL_NDX_1 YES N/A NO

SQL>


Note that the argument to CLEANUP_GIDX is the *Table Name*, not an Index Name.


Here I have demonstrated a TRUNCATE Partition, but the same method would be usable for a DROP Partition.
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The reverse of SPLITting a Partition is to MERGE two adjacent partitions.

I reverse the SPLIT that I did in the previous blog post.

SQL> l
1 select partition_name, tablespace_name, high_value
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4* order by partition_position
SQL> /

PARTITION_NAME TABLESPACE_NAME HIGH_VALUE
------------------------------ ------------------------------ --------------------------
P_2016 ARCHIVE_SALES_DATA TO_DATE(' 2017-01-01 00:00
P_2017 TBS_YEAR_2017 TO_DATE(' 2018-01-01 00:00
P_2018 TBS_YEAR_2018 TO_DATE(' 2019-01-01 00:00
P_2019_H1 TBS_YEAR_2019 TO_DATE(' 2019-07-01 00:00
P_2019_H2 TBS_YEAR_2019 TO_DATE(' 2020-01-01 00:00
P_2020 TBS_YEAR_2020 TO_DATE(' 2021-01-01 00:00
P_MAXVALUE USERS MAXVALUE

7 rows selected.

SQL>
SQL> alter table sales_data
2 merge partitions P_2019_H1, P_2019_H2
3 into partition P_2019
4 update indexes
5 /

Table altered.

SQL>
SQL> select partition_name, tablespace_name, high_value
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4 order by partition_position
5 /

PARTITION_NAME TABLESPACE_NAME HIGH_VALUE
------------------------------ ------------------------------ --------------------------
P_2016 ARCHIVE_SALES_DATA TO_DATE(' 2017-01-01 00:00
P_2017 TBS_YEAR_2017 TO_DATE(' 2018-01-01 00:00
P_2018 TBS_YEAR_2018 TO_DATE(' 2019-01-01 00:00
P_2019 HEMANT TO_DATE(' 2020-01-01 00:00
P_2020 TBS_YEAR_2020 TO_DATE(' 2021-01-01 00:00
P_MAXVALUE USERS MAXVALUE

6 rows selected.

SQL>


But, we find that the new Partition was created in the default "HEMANT"  tablespace !  So, we have to be careful about specifying target tablespace(s).

Let me reverse the action and try again.

SQL> alter table sales_data
2 split partition P_2019 at (to_date('01-JUL-2019','DD-MON-YYYY'))
3 into (partition P_2019_H1 tablespace TBS_YEAR_2019, partition P_2019_H2 tablespace TBS_YEAR_2019)
4 update indexes
5 /

Table altered.

SQL>
SQL> select partition_name, tablespace_name, high_value
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4 order by partition_position
5 /

PARTITION_NAME TABLESPACE_NAME HIGH_VALUE
------------------------------ ------------------------------ --------------------------
P_2016 ARCHIVE_SALES_DATA TO_DATE(' 2017-01-01 00:00
P_2017 TBS_YEAR_2017 TO_DATE(' 2018-01-01 00:00
P_2018 TBS_YEAR_2018 TO_DATE(' 2019-01-01 00:00
P_2019_H1 TBS_YEAR_2019 TO_DATE(' 2019-07-01 00:00
P_2019_H2 TBS_YEAR_2019 TO_DATE(' 2020-01-01 00:00
P_2020 TBS_YEAR_2020 TO_DATE(' 2021-01-01 00:00
P_MAXVALUE USERS MAXVALUE

7 rows selected.

SQL> alter table sales_data
2 merge partitions P_2019_H1, P_2019_H2
3 into partition P_2019 tablespace TBS_YEAR_2019
4 update indexes
5 /

Table altered.

SQL> select partition_name, tablespace_name, high_value
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4 order by partition_position
5 /

PARTITION_NAME TABLESPACE_NAME HIGH_VALUE
------------------------------ ------------------------------ --------------------------
P_2016 ARCHIVE_SALES_DATA TO_DATE(' 2017-01-01 00:00
P_2017 TBS_YEAR_2017 TO_DATE(' 2018-01-01 00:00
P_2018 TBS_YEAR_2018 TO_DATE(' 2019-01-01 00:00
P_2019 TBS_YEAR_2019 TO_DATE(' 2020-01-01 00:00
P_2020 TBS_YEAR_2020 TO_DATE(' 2021-01-01 00:00
P_MAXVALUE USERS MAXVALUE

6 rows selected.

SQL>


So, when running Table Partition DDL, be careful about the intended and actual target Tablespace(s).  (What about Index Partitions ?  The UPDATE INDEXES clause can specify target tablespaces for each Index Partition of each Index as well ... something like : (this is from the documentation on the ALTER TABLE command)
UPDATE INDEXES (cost_ix (PARTITION c_p1 tablespace tbs_02, 
PARTITION c_p2 tablespace tbs_03))
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Let's say the business anticipates growing sales volume in 2019 and new reporting requirements.  IT analyses the requirements and decides that the SALES_DATA Table that is currently Partitioned by YEAR, needs to be Partitioned by HALF-YEAR from 2019 onwards.

SQL> select partition_name, tablespace_name
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4 order by partition_position
5 /

PARTITION_NAME TABLESPACE_NAME
------------------------------ ------------------------------
P_2016 ARCHIVE_SALES_DATA
P_2017 TBS_YEAR_2017
P_2018 TBS_YEAR_2018
P_2019 TBS_YEAR_2019
P_2020 TBS_YEAR_2020
P_MAXVALUE USERS

6 rows selected.

SQL>
SQL> alter table sales_data
2 split partition P_2019 at (to_date('01-JUL-2019','DD-MON-YYYY'))
3 into (partition P_2019_H1, partition P_2019_H2)
4 update indexes
5 /

Table altered.

SQL>
SQL> col high_value format a26 trunc
SQL> select partition_name, tablespace_name, high_value
2 from user_tab_partitions
3 where table_name = 'SALES_DATA'
4 order by partition_position
5 /

PARTITION_NAME TABLESPACE_NAME HIGH_VALUE
------------------------------ ------------------------------ --------------------------
P_2016 ARCHIVE_SALES_DATA TO_DATE(' 2017-01-01 00:00
P_2017 TBS_YEAR_2017 TO_DATE(' 2018-01-01 00:00
P_2018 TBS_YEAR_2018 TO_DATE(' 2019-01-01 00:00
P_2019_H1 TBS_YEAR_2019 TO_DATE(' 2019-07-01 00:00
P_2019_H2 TBS_YEAR_2019 TO_DATE(' 2020-01-01 00:00
P_2020 TBS_YEAR_2020 TO_DATE(' 2021-01-01 00:00
P_MAXVALUE USERS MAXVALUE

7 rows selected.

SQL>


I used the UPDATE INDEXES clause to ensure that all (specifically Global) Indexes affected by the SPLIT are updated so that they don't go into an UNUSABLE state.

I could have optionally used a TABLESPACE clause for each of the two new Partitions P_2019_H1 and P_2019_H2


(Also see a previous BlogPost on using SPLIT PARTITION to add a new Partition at the "end" of the table by splitting the last Partition)
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Here's a compilation of some useful data dictionary queries on the implementation of Partitioning.

REM  List all Partitioned Tables in the database (or filter by OWNER in the WHERE clause)
REM Note that the last column is the *defined* default subpartition count
select owner, table_name, partitioning_type, subpartitioning_type, partition_count,
def_subpartition_count as default_subpart_count
from dba_part_tables
order by owner, table_name


REM List all Partitioned Indexes in the database (or filter by OWNER in the WHERE clause)
REM Note that the last column is the *defined* default subpartition count
select owner, index_name, table_name, partitioning_type, subpartitioning_type, partition_count,
def_subpartition_count as default_subpart_count
from dba_part_indexes
order by owner, index_name


REM List Partition Key Columns for all Partitioned Tables
REM (or filter by OWNER or NAME (NAME is TABLE_NAME when object_type='TABLE'))
REM Need to order by column_position as Partition Key may consist of multiple columns
select owner, name, column_name
from dba_part_key_columns
where object_type = 'TABLE'
order by owner, name, column_position


REM List Partition Key Columns for Table SubPartitions
REM (or filter by OWNER or NAME (NAME is TABLE_NAME when object_type='TABLE'))
REM Need to order by column_position as SubPartition Key may consist of multiple columns
select owner, name, column_name
from dba_subpart_key_columns
where object_type = 'TABLE'
order by owner, name, column_position


REM List Partition Key Columns for Index SubPartitions
REM (or filter by OWNER or NAME (NAME is INDEX_NAME when object_type='INDEX'))
REM Need to order by column_position as SubPartition may consist of multiple columns
select owner, name, column_name
from dba_subpart_key_columns
where object_type = 'INDEX'
order by owner, name, column_position


REM List all Table Partitions (or filter by TABLE_OWNER or TABLE_NAME in the WHERE clause)
REM Need to order by partition_position
select table_owner, table_name, partition_name, high_value, tablespace_name, num_rows, last_analyzed
from dba_tab_partitions
order by table_owner, table_name, partition_position


REM List all Table SubPartitions (or filter by TABLE_OWNER or TABLE_NAME in the WHERE clause)
select table_owner, table_name, partition_name, subpartition_name, high_value, tablespace_name, num_rows, last_analyzed
from dba_tab_subpartitions
order by table_owner, table_name, subpartition_position


REM List all Index Partitions (or filter by INDEX_OWNER or INDEX_NAME in the WHERE clause)
REM Need to order by partition_position
REM Note : For Table Names, you have to join back to dba_indexes
select index_owner, index_name, partition_name, tablespace_name, num_rows, last_analyzed
from dba_ind_partitions
order by index_owner, index_name, partition_position


REM List all Index SubPartitions (or filter by INDEX_OWNER or INDEX_NAME in the WHERE clause)
select index_owner, index_name, partition_name, subpartition_name, tablespace_name, num_rows, last_analyzed
from dba_ind_subpartitions
order by index_owner, index_name, subpartition_position


I have listed only a few columns from the data dictionary views of interest.  You may extract more information by referencing other columns or joining to other data dictionary views.
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Oracle allows Composite Partitioning where a Partition can, itself, be Sub-Partitioned.  Each SubPartition is a distinct segment (allocation of physical blocks) while the Partition itself remains a logical definition without a segment.

Composite Partitioning can comprise of :


  • Range-Hash  
  • Range-List  
  • Range-Range
  • List-Range
  • List-Hash
  • List-List
  • Interval-Hash
  • Interval-List
  • Interval-Range

Here is one example of Range-List Partitioning :

SQL> drop table my_sales_table; Table dropped. SQL>
SQL> alter session set deferred_segment_creation=FALSE;

Session altered.

SQL>
SQL> l
1 create table my_sales_table
2 (invoice_id number(16) primary key,
3 invoice_date date,
4 region_code varchar2(5),
5 invoice_amount number)
6 partition by range (invoice_date)
7 subpartition by list (region_code)
8 subpartition template
9 (
10 subpartition US values ('US') tablespace tbs_US,
11 subpartition EMEA values ('EMEA') tablespace tbs_EMEA,
12 subpartition ASIA values ('ASIA') tablespace tbs_ASIA,
13 subpartition OTHERS values (DEFAULT) tablespace tbs_OTHERS)
14 (
15 partition p_2018 values less than (to_date('01-JAN-2019','DD-MON-YYYY')),
16 partition p_2019 values less than (to_date('01-JAN-2020','DD-MON-YYYY'))
17* )
SQL> /

Table created.

SQL>
SQL> select table_name, partition_name, subpartition_name
2 from user_tab_subpartitions
3 where table_name = 'MY_SALES_TABLE'
4 /

TABLE_NAME PARTITION_NAME SUBPARTITION_NAME
------------------------------ --------------- ------------------------------
MY_SALES_TABLE P_2018 P_2018_US
MY_SALES_TABLE P_2018 P_2018_EMEA
MY_SALES_TABLE P_2018 P_2018_ASIA
MY_SALES_TABLE P_2018 P_2018_OTHERS
MY_SALES_TABLE P_2019 P_2019_US
MY_SALES_TABLE P_2019 P_2019_EMEA
MY_SALES_TABLE P_2019 P_2019_ASIA
MY_SALES_TABLE P_2019 P_2019_OTHERS

8 rows selected.

SQL>
SQL> l
1 select segment_name, segment_type, partition_name, tablespace_name
2 from user_segments
3 where segment_name = 'MY_SALES_TABLE'
4* order by 1,2,3
SQL> /

SEGMENT_NAME SEGMENT_TYPE PARTITION_NAME TABLESPACE_N
--------------- ------------------ --------------- ------------
MY_SALES_TABLE TABLE SUBPARTITION P_2018_ASIA TBS_ASIA
MY_SALES_TABLE TABLE SUBPARTITION P_2018_EMEA TBS_EMEA
MY_SALES_TABLE TABLE SUBPARTITION P_2018_OTHERS TBS_OTHERS
MY_SALES_TABLE TABLE SUBPARTITION P_2018_US TBS_US
MY_SALES_TABLE TABLE SUBPARTITION P_2019_ASIA TBS_ASIA
MY_SALES_TABLE TABLE SUBPARTITION P_2019_EMEA TBS_EMEA
MY_SALES_TABLE TABLE SUBPARTITION P_2019_OTHERS TBS_OTHERS
MY_SALES_TABLE TABLE SUBPARTITION P_2019_US TBS_US

8 rows selected.

SQL>


Note how the actual SubPartition Names are auto-created by Oracle using the composite of the Partition Name  (P_2018, P_2019) and the SubPartition Name (from the SubPartition Template).

In this case, the names that are SubPartition in USER_TAB_SUBPARTITIONS appear as PARTITION_NAME in USER_SEGMENTS because each of the two logical Partitions (P_2018, P_2019) don't actually have their own Segments.


Note :  I set "deferred_segment_creation" to FALSE so that all the Segments would be created upfront even if they are not populated. "deferred_segment_creation" is an 11g feature.
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