Partitioning of Oracle Tables

This article organizes the concepts and operations of partitioned tables from the following aspects:
1. Table space and the concept of partitioned tables
2. The specific role of table partitioning
3. Advantages and disadvantages of table partitioning
4. Several types of table partitioning and how to operate them
5. Maintenance Operations on table partitioning.
(1) The concept of table space and partitioned tables
Tablespace: is a collection of one or more data files, all of which are stored in the specified table space, but are primarily tables, so called table spaces.
Partition table:
When the amount of data in the table is increasing, the query data slows down and the performance of the application degrades, so you should consider partitioning the table. After the table is partitioned, the logical table is still a complete table, but the data in the table is physically stored in multiple table spaces (physical files) so that querying the data does not always scan the entire table.

(2). The specific role of table partitioning
Oracle's table partitioning capabilities bring great benefits to a wide variety of applications by improving manageability, performance, and availability. In general, partitioning can greatly improve the performance of certain queries and maintenance operations. In addition, partitioning can greatly simplify common administrative tasks, and partitioning is a key tool for building gigabytes of data systems or ultra-high availability systems.

The partitioning feature can further subdivide a table, index, or index organization table into segments, where the segments of these database objects are called partitions. Each partition has its own name, and you can choose your own storage features. From the database administrator's point of view, a partitioned object has multiple segments that can be collectively managed or managed separately, which gives the database manager considerable flexibility in managing the objects after the partition. However, from the application's point of view, the partitioned table is exactly the same as the non-partitioned table, and no modifications are required to access the partitioned table using the SQL DML command.

When to use partitioned tables:
1, the size of the table is more than 2GB.
2, the table contains historical data, new data is added to the new partition.

(3). Table Partitioning Advantages and disadvantages
Table partitioning has the following advantages:
1. Improve query performance: Queries on partitioned objects can search only the partitions they care about and improve the retrieval speed.
2. Enhanced usability: If one partition of the table fails, the data of the table in other partitions is still available;
3, Maintenance Convenience: If a partition of the table fails, you need to repair the data, only repair the partition;
4. Balanced I/O: Different partitions can be mapped to disk to balance I/O and improve overall system performance.

Disadvantages:
Partition Table Related: Existing tables have no methods that can be converted directly into partitioned tables. However, Oracle provides the ability to redefine tables online.

(4). Several types of table partitioning and how to do it
I. Scope partitioning:
A range partition maps data to each partition based on its scope, which is determined by the partition key you specify when you create the partition. This partitioning method is most commonly used, and the partitioning key often takes the date. For example, you might partition sales data by month.
When using range partitioning, consider the following rules:
1. Each partition must have a values less then clause that specifies an upper value that is not included in the partition. Any record of the partition key that is equal to or greater than this upper value is added to the next higher partition.
2. All partitions, except the first one, will have an implicit lower value, which is the upper limit of the previous partition of this partition.
3. In the highest partition, MaxValue is defined. The MaxValue represents an indeterminate value. This value is higher than the value of any partition key in the other partition, and it can be understood to be higher than the value less or less that is specified in any partition, including null values.
Example one:
Suppose there is a customer table with data 200000 rows, we partition this table through CUSTOMER_ID, each partition stores 100000 rows, and we save each partition in a separate tablespace so that the data file can span multiple physical disks. Here is the code to create the table and partition, as follows:
CREATE TABLE CUSTOMER
(
customer_id number not NULL PRIMARY KEY,
First_Name VARCHAR2 (+) not NULL,
Last_Name VARCHAR2 (+) not NULL,
PHONE VARCHAR2 () not NULL,
EMAIL VARCHAR2 (80),
STATUS CHAR (1)
)
PARTITION by RANGE (customer_id)
(
PARTITION cus_part1 VALUES less THAN (100000) tablespace cus_ts01,
PARTITION cus_part2 VALUES less THAN (200000) tablespace CUS_TS02
)
Example two: divided by time
CREATE TABLE order_activities
(
ORDER_ID Number (7) is not NULL,
Order_date DATE,
Total_amount number,
CUSTOTMER_ID Number (7),
PAID CHAR (1)
)
PARTITION by RANGE (order_date)
(
PARTITION ord_act_part01 VALUES Less THAN (to_date (' 01-may-2003 ', ' dd-mon-yyyy ')) tablespaceord_ts01,
PARTITION ord_act_part02 VALUES Less THAN (to_date (' 01-jun-2003 ', ' dd-mon-yyyy ') tablespace ord_ts02,
PARTITION ord_act_part02 VALUES Less THAN (to_date (' 01-jul-2003 ', ' dd-mon-yyyy ') tablespace ord_ts03
)
Example three: MAXVALUE
CREATE TABLE rangetable
(
IDD INT PRIMARY KEY,
Iname VARCHAR (10),
Grade INT
)
PARTITION by RANGE (grade)
(
PARTITION part1 VALUES Less then (tablespace part1_tb),
PARTITION part2 VALUES less then (MAXVALUE) tablespace PART2_TB
);

Two. List partition:
This partition is characterized by a column with only a few values, based on which we can take the list partition.
Example One
CREATE TABLE Problem_tickets
(
PROBLEM_ID Number (7) Not NULL PRIMARY KEY,
DESCRIPTION VARCHAR2 (2000),
CUSTOMER_ID Number (7) is not NULL,
Date_entered DATE not NULL,
STATUS VARCHAR2 (20)
)
PARTITION by LIST (STATUS)
(
PARTITION prob_active VALUES (' ACTIVE ') tablespace prob_ts01,
PARTITION prob_inactive VALUES (' INACTIVE ') tablespace PROB_TS02
Example Two
CREATE TABLE listtable
(
ID INT PRIMARY KEY,
Name VARCHAR (20),
Area VARCHAR (10)
)
PARTITION by LIST (area)
(
PARTITION part1 VALUES (' Guangdong ', ' Beijing ') tablespace PART1_TB,
PARTITION part2 VALUES (' Shanghai ', ' Nanjing ') tablespace PART2_TB
);
)

Three. Hash partition:
This type of partitioning uses a hashing algorithm on column values to determine which partition the rows are placed in. Hash partitioning is recommended when the value of the column does not have an appropriate condition.
A hash partition is a type of partition that distributes data evenly by specifying the partition number, because the partitions are identical in size by hashing on the I/O device.
Example one:
CREATE TABLE hash_table
(
COL Number (8),
INF VARCHAR2 (100)
)
PARTITION by HASH (COL)
(
PARTITION PART01 tablespace hash_ts01,
PARTITION PART02 tablespace HASH_TS02,
PARTITION PART03 tablespace Hash_ts03
)
Shorthand:
CREATE TABLE EMP
(
Empno Number (4),
Ename VARCHAR2 (30),
Sal number
)
PARTITION by HASH (empno) Partitions 8
STORE in (EMP1,EMP2,EMP3,EMP4,EMP5,EMP6,EMP7,EMP8);

Hash partition The main mechanism is based on the hash algorithm to calculate the specific record should be inserted into which partition, hash algorithm is the most important hash function, Oracle if you want to use the hash partition, only specify the number of partitions. It is recommended that the number of partitions be 2 N, which makes the data distribution more evenly between partitions.

Four. Combined range hash Partition
This partition is based on a range partition and a list partition, where the table is first partitioned by a column, then a list is partitioned by a column, and the partitions in the partition are called sub-partitions.
CREATE TABLE SALES
(
product_id VARCHAR2 (5),
Sales_date DATE,
Sales_cost Number (10),
STATUS VARCHAR2 (20)
)
PARTITION by RANGE (sales_date) subpartition by LIST (STATUS)
(
PARTITION P1 VALUES Less THAN (to_date (' 2003-01-01 ', ' yyyy-mm-dd ') tablespace rptfact2009
(
Subpartition p1sub1 VALUES (' ACTIVE ') tablespace rptfact2009,
Subpartition p1sub2 VALUES (' INACTIVE ') tablespace rptfact2009
),
PARTITION P2 VALUES Less THAN (to_date (' 2003-03-01 ', ' yyyy-mm-dd ') tablespace rptfact2009
(
Subpartition p2sub1 VALUES (' ACTIVE ') tablespace rptfact2009,
Subpartition p2sub2 VALUES (' INACTIVE ') tablespace rptfact2009
)
)

Five. Composite range Hash Partition:
This partition is based on range partitioning and hash partitioning, where the table is first scoped by a column and then hashed by a column.
CREATE TABLE Dinya_test
(
TRANSACTION_ID Number primary Key,
ITEM_ID Number (8) is not NULL,
Item_description VARCHAR2 (300),
Transaction_date Date
)
Partition by Range (transaction_date) subpartition by hash (transaction_id) Subpartitions 3 store in (Dinya_space01,dinya_ SPACE02,DINYA_SPACE03)
(
Partition part_01 values less than (to_date (' 2006-01-01 ', ' yyyy-mm-dd ')),
Partition part_02 values less than (to_date (' 2010-01-01 ', ' yyyy-mm-dd ')),
Partition part_03 values less than (MaxValue)
);

(5). Some maintenance actions related to table partitioning:
First, add the partition
The following code adds a P3 partition to the sales table
ALTER TABLE SALES ADD PARTITION P3 VALUES less THAN (to_date (' 2003-06-01 ', ' yyyy-mm-dd '));
Note: The above partition boundaries should be added above the last partition bounds.
The following code adds a P3SUB1 sub-partition to the P3 partition of the sales table
ALTER TABLE SALES MODIFY PARTITION P3 ADD subpartition p3sub1 VALUES (' complete ');
Second, delete the partition
The following code removes the P3 table partition:
ALTER TABLE SALES DROP PARTITION P3;
The P4SUB1 sub-partition was removed in the following code:
ALTER TABLE SALES DROP subpartition p4sub1;
Note: If the deleted partition is the only partition in the table, then this partition will not be deleted and you must delete the table if you want to delete this partition.
Third, truncate the partition
Truncating a partition means deleting data from a partition, and does not delete the partition, nor does it delete data from other partitions. You can truncate a table even if it has only one partition. Truncate the partition with the following code:
ALTER TABLE SALES TRUNCATE PARTITION P2;
Truncate the sub-partition with the following code:
ALTER TABLE SALES TRUNCATE subpartition p2sub2;
Iv. Merging of partitions
Merging partitions is the merging of adjacent partitions into a single partition, with the result that partitions are bounded by higher partitions, and it is worth noting that partitions cannot be merged into lower-bound partitions. The following code implements the merge of the P1 P2 partition:
ALTER TABLE SALES MERGE partitions p1,p2 into PARTITION P2;
V. Splitting partitions
Split partition splits a partition into two new partitions, after which the original partition no longer exists. Note You cannot split a hash-type partition.
ALTER TABLE SALES sblit PARTITION P2 at (to_date (' 2003-02-01 ', ' yyyy-mm-dd ')] into (PARTITION p21,partition P22);
Vi. junction Zoning (Coalesca)
Combined partitioning is the data in the hash partition into other partitions, when the data in the hash partition is relatively large, you can increase the hash partition and then engage, it is worth noting that the bonded partition can only be used in the hash partition. Use the following code to make a bonded partition:
ALTER TABLE SALES Coalesca PARTITION;
Vii. Renaming table Partitions
The following code changes P21 to P2
ALTER TABLE SALES RENAME PARTITION P21 to P2;
Eight, related inquiries
Cross-partition queries
Select SUM (*) from
(SELECT COUNT (*) cn from T_TABLE_SS PARTITION (p200709_1)
UNION ALL
Select COUNT (*) cn from T_TABLE_SS PARTITION (p200709_2)
);
How many partitions are on the query table
SELECT * from user_tab_partitions WHERE table_name= ' TableName '
Querying index information
Select Object_name,object_type,tablespace_name,sum (Value)
From V$segment_statistics
where Statistic_name in (' physical reads ', ' physical write ', ' logical reads ') and object_type= ' INDEX '
GROUP BY Object_name,object_type,tablespace_name
ORDER BY 4 DESC

--Displays information about all partitioned tables in the database:
SELECT * FROM Dba_part_tables

--Displays all partition table information that the current user can access:
SELECT * FROM All_part_tables

--Displays information about all the partition tables for the current user:
SELECT * FROM User_part_tables

--Display table partition information displays detailed partition information for all partitioned tables in the database:
SELECT * FROM Dba_tab_partitions

--Displays detailed partitioning information for all partitioned tables that the current user can access:
SELECT * FROM All_tab_partitions

--Displays detailed partitioning information for all partition tables for the current user:
SELECT * FROM User_tab_partitions

--Display sub-partition information displays sub-partition information for all the combined partition tables of the database:
SELECT * FROM Dba_tab_subpartitions

--Displays sub-partition information for all the combined partitioned tables that the current user can access:
SELECT * FROM All_tab_subpartitions

--Displays sub-partition information for all the combined partition tables of the current user:
SELECT * FROM User_tab_subpartitions

--Show partition column displays the partition column information for all partitioned tables in the database:
SELECT * FROM Dba_part_key_columns

--Displays the partition column information for all partitioned tables that the current user can access:
SELECT * FROM All_part_key_columns

--Displays the partition column information for all partition tables for the current user:
SELECT * FROM User_part_key_columns

--Show sub-partition columns displays sub-partition column information for all partitioned tables in the database:
SELECT * FROM Dba_subpart_key_columns

--Displays sub-partition column information for all partitioned tables that the current user can access:
SELECT * FROM All_subpart_key_columns

--Displays sub-partition column information for all partitioned tables of the current user:
SELECT * FROM User_subpart_key_columns

--How to query out all the partitioned tables in the Oracle database
SELECT * from User_tables a where a.partitioned= ' YES '

--deleting data from a table is
TRUNCATE TABLE table_name;

--Delete partition table data for a partition is
ALTER TABLE TABLE_NAME TRUNCATE PARTITION P5;


PS: When update changes the partition that the data belongs to, you must give the table row movement permission.
ALTER TABLE test_partition_tab enable/disable row movement;
Update Partition field, change the partition, the data in the internal change is through the source data into the new partition, new data updates, the source of old data deleted steps, so rowid will change; The data index will also be re-run.

Partitioning of Oracle Tables