online-merge-partition-and-subpartition-18c

Online MERGE PARTITION and MERGE SUBPARTITION in Oracle Database 18c

In Oracle Database 18c the MERGE PARTITION and MERGE SUBPARTITION
operations on heap tables can be performed online so they don't block
DML. This is done by the addition of the ONLINE keyword, which also
causes local and global indexes to be updated without having to specify
the UPDATE INDEXES clause.

Merge Partition
* [46]Online MERGE PARTITION
* [47]Online MERGE SUBPARTITION

Related articles.
* [48]All Partitioning Articles
* [49]Partitioning Enhancements in Oracle Database 12c Release 2
(12.2)
* [50]Online Operation Enhancements in Oracle Database 12c Release 1
(12.1)

Online MERGE PARTITION

Create a partitioned table with a three partitions, along with a global
and partitioned index.
DROP TABLE t1 PURGE;

CREATE TABLE t1 (
id NUMBER,
code VARCHAR2(10),
description VARCHAR2(50),
created_date DATE,
CONSTRAINT t1_pk PRIMARY KEY (id)
)
PARTITION BY RANGE (created_date)
(
PARTITION t1_2016 VALUES LESS THAN (TO_DATE('01-JAN-2017 00:00:00', 'DD-MON-YY
YY HH24:MI:SS')),
PARTITION t1_2017 VALUES LESS THAN (TO_DATE('01-JAN-2018 00:00:00', 'DD-MON-YY
YY HH24:MI:SS')),
PARTITION t1_2018 VALUES LESS THAN (MAXVALUE)
);


CREATE INDEX t1_created_date_idx ON t1 (created_date) LOCAL;
CREATE INDEX t1_code_idx ON t1 (code);


INSERT INTO t1 VALUES ( 1, 'ONE', 'Description for ONE', TO_DATE('01-FEB-2016'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 2, 'TWO', 'Description for ONE', TO_DATE('01-FEB-2016'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 3, 'THREE', 'Description for ONE', TO_DATE('01-FEB-2016'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 4, 'FOUR', 'Description for ONE', TO_DATE('01-FEB-2016'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 5, 'ONE', 'Description for ONE', TO_DATE('01-FEB-2017'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 6, 'TWO', 'Description for ONE', TO_DATE('01-FEB-2017'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 7, 'THREE', 'Description for ONE', TO_DATE('01-FEB-2017'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 8, 'FOUR', 'Description for ONE', TO_DATE('01-FEB-2017'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES ( 9, 'ONE', 'Description for ONE', TO_DATE('01-FEB-2018'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES (10, 'TWO', 'Description for ONE', TO_DATE('01-FEB-2018'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES (11, 'THREE', 'Description for ONE', TO_DATE('01-FEB-2018'
,'DD-MON-YYYY'));
INSERT INTO t1 VALUES (12, 'FOUR', 'Description for ONE', TO_DATE('01-FEB-2018'
,'DD-MON-YYYY'));
COMMIT;

EXEC DBMS_STATS.gather_table_stats(USER, 't1', cascade => TRUE);

Display the current table partitions and index information.
-- Table partitions.
COLUMN table_name FORMAT A30
COLUMN partition_name FORMAT A30

SELECT table_name,
partition_name,
num_rows
FROM user_tab_partitions
ORDER BY 1, 2;

TABLE_NAME PARTITION_NAME NUM_ROWS
------------------------------ ------------------------------ ----------
T1 T1_2016 4
T1 T1_2017 4
T1 T1_2018 4

SQL>


-- Indexes.
COLUMN index_name FORMAT A30
COLUMN partitioned FORMAT A11

SELECT index_name,
partitioned,
status
FROM user_indexes
ORDER BY 1;

INDEX_NAME PARTITIONED STATUS
------------------------------ ----------- --------
T1_CODE_IDX NO VALID
T1_CREATED_DATE_IDX YES N/A
T1_PK NO VALID

SQL>


-- Index partitions.
SELECT index_name,
partition_name,
status
FROM user_ind_partitions
ORDER BY 1, 2;

INDEX_NAME PARTITION_NAME STATUS
------------------------------ ------------------------------ --------
T1_CREATED_DATE_IDX T1_2016 USABLE
T1_CREATED_DATE_IDX T1_2017 USABLE
T1_CREATED_DATE_IDX T1_2018 USABLE

SQL>

Perform an online operation to merge the T1_2016 partition into the
T1_2017 partition.
ALTER TABLE t1
MERGE
PARTITIONS t1_2016, t1_2017
INTO PARTITION t1_2017
ONLINE;

EXEC DBMS_STATS.gather_table_stats(USER, 't1', cascade => TRUE);

Display the current status of the table partitions and indexes. Notice
both the global and local indexes are left in a usable state without
having to specify the UPDATE INDEXES clause.
-- Table partitions.
COLUMN table_name FORMAT A30
COLUMN partition_name FORMAT A30

SELECT table_name,
partition_name,
num_rows
FROM user_tab_partitions
ORDER BY 1, 2;

TABLE_NAME PARTITION_NAME NUM_ROWS
------------------------------ ------------------------------ ----------
T1 T1_2017 8
T1 T1_2018 4

SQL>


-- Indexes.
COLUMN index_name FORMAT A30
COLUMN partitioned FORMAT A11

SELECT index_name,
partitioned,
status
FROM user_indexes
ORDER BY 1;

INDEX_NAME PARTITIONED STATUS
------------------------------ ----------- --------
T1_CODE_IDX NO VALID
T1_CREATED_DATE_IDX YES N/A
T1_PK NO VALID

SQL>


-- Index partitions.
SELECT index_name,
partition_name,
status
FROM user_ind_partitions
ORDER BY 1, 2;

INDEX_NAME PARTITION_NAME STATUS
------------------------------ ------------------------------ --------
T1_CREATED_DATE_IDX T1_2017 USABLE
T1_CREATED_DATE_IDX T1_2018 USABLE

SQL>

For a comparison, perform an offline operation to merge the T1_2017
partition into the T1_2018 partition.
ALTER TABLE t1
MERGE
PARTITIONS t1_2017, t1_2018
INTO PARTITION t1_2018;

EXEC DBMS_STATS.gather_table_stats(USER, 't1', cascade => TRUE);

Display the current status of the table partitions and indexes. Notice
both the global and local indexes on the affected partitions are left
in a unusable state because we didn't specify the UPDATE INDEXES clause
or ONLINE keyword.
-- Table partitions.
COLUMN table_name FORMAT A30
COLUMN partition_name FORMAT A30

SELECT table_name,
partition_name,
num_rows
FROM user_tab_partitions
ORDER BY 1, 2;

TABLE_NAME PARTITION_NAME NUM_ROWS
------------------------------ ------------------------------ ----------
T1 T1_2018 12

SQL>


-- Indexes.
COLUMN index_name FORMAT A30
COLUMN partitioned FORMAT A11

SELECT index_name,
partitioned,
status
FROM user_indexes
ORDER BY 1;

INDEX_NAME PARTITIONED STATUS
------------------------------ ----------- --------
T1_CODE_IDX NO UNUSABLE
T1_CREATED_DATE_IDX YES N/A
T1_PK NO UNUSABLE

SQL>


-- Index partitions.
COLUMN partition_name FORMAT A30

SELECT index_name,
partition_name,
status
FROM user_ind_partitions
ORDER BY 1, 2;

INDEX_NAME PARTITION_NAME STATUS
------------------------------ ------------------------------ --------
T1_CREATED_DATE_IDX T1_2018 UNUSABLE

SQL>

Online MERGE SUBPARTITION

Create a subpartitioned table with two partitions, each with three
subpartitions, along with a global and partitioned index.
DROP TABLE t1 PURGE;

CREATE TABLE t1 (
id NUMBER,
code VARCHAR2(10),
description VARCHAR2(50),
created_date DATE,
CONSTRAINT t1_pk PRIMARY KEY (id)
)
PARTITION BY RANGE (created_date)
SUBPARTITION BY LIST (code)
SUBPARTITION TEMPLATE (
SUBPARTITION small VALUES ('ONE'),
SUBPARTITION medium VALUES ('TWO', 'THREE'),
SUBPARTITION others VALUES (DEFAULT)
)
(
PARTITION year_2017 VALUES LESS THAN ( TO_DATE('01-JAN-2018','DD-MON-YYYY')),
PARTITION year_2018 VALUES LESS THAN ( TO_DATE('01-JAN-2019','DD-MON-YYYY'))
);

CREATE INDEX t1_created_date_idx ON t1 (created_date) LOCAL;
CREATE INDEX t1_code_idx ON t1 (code);

INSERT INTO t1 VALUES (1, 'ONE', 'Description for ONE', TO_DATE('01-JUL-2017',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (2, 'TWO', 'Description for ONE', TO_DATE('01-JUL-2017',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (3, 'THREE', 'Description for ONE', TO_DATE('01-JUL-2017',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (4, 'FOUR', 'Description for ONE', TO_DATE('01-JUL-2017',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (5, 'ONE', 'Description for ONE', TO_DATE('01-JUL-2018',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (6, 'TWO', 'Description for ONE', TO_DATE('01-JUL-2018',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (7, 'THREE', 'Description for ONE', TO_DATE('01-JUL-2018',
'DD-MON-YYYY'));
INSERT INTO t1 VALUES (8, 'FOUR', 'Description for ONE', TO_DATE('01-JUL-2018',
'DD-MON-YYYY'));
COMMIT;

EXEC DBMS_STATS.gather_table_stats(USER, 'T1', cascade => TRUE);

Display the current table partition and index information.
SET LINESIZE 120

COLUMN table_name FORMAT A30
COLUMN partition_name FORMAT A30
COLUMN subpartition_name FORMAT A30

-- Table subpartitions.
SELECT table_name,
partition_name,
subpartition_name,
num_rows
FROM user_tab_subpartitions
ORDER BY 1,2,3;

TABLE_NAME PARTITION_NAME SUBPARTITION_NAME
NUM_ROWS
------------------------------ ------------------------------ ------------------
------------ ----------
T1 YEAR_2017 YEAR_2017_MEDIUM
2
T1 YEAR_2017 YEAR_2017_OTHERS
1
T1 YEAR_2017 YEAR_2017_SMALL
1
T1 YEAR_2018 YEAR_2017_MEDIUM
2
T1 YEAR_2018 YEAR_2017_OTHERS
1
T1 YEAR_2018 YEAR_2017_SMALL
1

SQL>


-- Indexes.
SELECT index_name,
partitioned,
status
FROM user_indexes
ORDER BY 1;

INDEX_NAME PARTITIONED STATUS
------------------------------ ----------- --------
T1_CODE_IDX NO VALID
T1_CREATED_DATE_IDX YES N/A
T1_PK NO VALID

SQL>


-- Index subpartitions.
SELECT index_name,
partition_name,
subpartition_name,
status
FROM user_ind_subpartitions
ORDER BY 1,2,3;

INDEX_NAME PARTITION_NAME SUBPARTITION_NAME
STATUS
------------------------------ ------------------------------ ------------------
------------ --------
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_MEDIUM
USABLE
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_OTHERS
USABLE
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_SMALL
USABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_MEDIUM
USABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_OTHERS
USABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_SMALL
USABLE

SQL>

Perform an online operation to merge the YEAR_2017_SMALL subpartition
into the YEAR_2017_MEDIUM subpartition.
ALTER TABLE t1
MERGE
SUBPARTITIONS year_2017_small, year_2017_medium
INTO SUBPARTITION year_2017_medium
ONLINE;

EXEC DBMS_STATS.gather_table_stats(USER, 'T1', cascade => TRUE);

Display the current status of the table subpartitions and indexes.
Notice both the global and local indexes are left in a usable state
without having to specify the UPDATE INDEXES clause.
-- Table subpartitions.
SELECT table_name,
partition_name,
subpartition_name,
num_rows
FROM user_tab_subpartitions
ORDER BY 1,2,3;

TABLE_NAME PARTITION_NAME SUBPARTITION_NAME
NUM_ROWS
------------------------------ ------------------------------ ------------------
------------ ----------
T1 YEAR_2017 YEAR_2017_MEDIUM
3
T1 YEAR_2017 YEAR_2017_OTHERS
1
T1 YEAR_2018 YEAR_2017_MEDIUM
2
T1 YEAR_2018 YEAR_2017_OTHERS
1
T1 YEAR_2018 YEAR_2017_SMALL
1

SQL>


-- Indexes.
SELECT index_name,
partitioned,
status
FROM user_indexes
ORDER BY 1;

INDEX_NAME PARTITIONED STATUS
------------------------------ ----------- --------
T1_CODE_IDX NO VALID
T1_CREATED_DATE_IDX YES N/A
T1_PK NO VALID

SQL>


-- Index subpartitions.
SELECT index_name,
partition_name,
subpartition_name,
status
FROM user_ind_subpartitions
ORDER BY 1,2,3;

INDEX_NAME PARTITION_NAME SUBPARTITION_NAME
STATUS
------------------------------ ------------------------------ ------------------
------------ --------
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_MEDIUM
USABLE
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_OTHERS
USABLE
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2018_MEDIUM
USABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_OTHERS
USABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_SMALL
USABLE

SQL>

For a comparison, perform an offline operation to merge the
YEAR_2018_SMALL subpartition into the YEAR_2018_MEDIUM subpartition.
ALTER TABLE t1
MERGE
SUBPARTITIONS year_2018_small, year_2018_medium
INTO SUBPARTITION year_2018_medium;

EXEC DBMS_STATS.gather_table_stats(USER, 'T1', cascade => TRUE);

Display the current status of the table subpartitions and indexes.
Notice both the global and local indexes on the affected subpartition
are left in a unusable state because we didn't specify the UPDATE
INDEXES clause or ONLINE keyword.
-- Table subpartitions.
SELECT table_name,
partition_name,
subpartition_name,
num_rows
FROM user_tab_subpartitions
ORDER BY 1,2,3;

TABLE_NAME PARTITION_NAME SUBPARTITION_NAME
NUM_ROWS
------------------------------ ------------------------------ ------------------
------------ ----------
T1 YEAR_2017 YEAR_2017_MEDIUM
3
T1 YEAR_2017 YEAR_2017_OTHERS
1
T1 YEAR_2018 YEAR_2017_MEDIUM
3
T1 YEAR_2018 YEAR_2017_OTHERS
1

SQL>


-- Indexes.
SELECT index_name,
partitioned,
status
FROM user_indexes
ORDER BY 1;

INDEX_NAME PARTITIONED STATUS
------------------------------ ----------- --------
T1_CODE_IDX NO UNUSABLE
T1_CREATED_DATE_IDX YES N/A
T1_PK NO UNUSABLE

SQL>


-- Index subpartitions.
SELECT index_name,
partition_name,
subpartition_name,
status
FROM user_ind_subpartitions
ORDER BY 1,2,3;

INDEX_NAME PARTITION_NAME SUBPARTITION_NAME
STATUS
------------------------------ ------------------------------ ------------------
------------ --------
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_MEDIUM
USABLE
T1_CREATED_DATE_IDX YEAR_2017 YEAR_2017_OTHERS
USABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_MEDIUM
UNUSABLE
T1_CREATED_DATE_IDX YEAR_2018 YEAR_2018_OTHERS
USABLE

SQL>

For more information see:
* [51]About Merging Partitions and Subpartitions
* [52]ALTER TABLE
* [53]All Partitioning Articles
* [54]Partitioning Enhancements in Oracle Database 12c Release 2
(12.2)
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Source .... : https://oracle-base.com/articles/18c/online-merge-partition-and-subpartition-18c
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