Oracle Table Partitioning

The concepts and operations of partitioned tables are organized in the following ways:

1. The concept of table spaces and 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. Table space and the concept of partitioned tables

Table Space:

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, and new data is added to the new partition.

3. Advantages and disadvantages of table partitioning

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 for the table on the other partitions is still available;

3) Easy maintenance: If a partition of the table fails, the data needs to be repaired, only the partition can be repaired;

4) Balanced I/O: Different partitions can be mapped to disk to balance I/O and improve overall system performance.

Disadvantages:

Partitioned 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 operate them

1. Range 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 1:

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 (a) not        null,    EMAIL        VARCHAR2,    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 2: Divided by Time

CREATE TABLE order_activities (order_id number      (7) 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 ' , ' 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 3:maxvalue

CREATE TABLE rangetable (  IDD   INT PRIMARY KEY,  iname VARCHAR (Ten),  grade INT) PARTITION  by  RANGE (Grade) (      PARTITION  part1 VALUES less then  () tablespace  PART1_TB,      PARTITION  part2 VALUES less then  (MAXVALUE) tablespace  PART2_TB);

2. List partition:

This partition is characterized by a column with only a few values, based on which we can take the list partition.

Example 1

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 is not null,    status       VARCHAR2 ()) PARTITION by LIST (status) (      PARTITION prob_active   values (' ACTIVE ') tablespace prob_ts01,      PARTITION prob_inactive values (' INACTIVE ') Tablespace PROB_TS02

Example 2

CREATE  TABLE  listtable (    ID    INT  PRIMARY  KEY,    name  VARCHAR),  area VARCHAR (+) PARTITION  by LIST (area) (    PARTITION  part1 VALUES (' Guangdong ', ' Beijing ') Tablespace  part1_tb,    PARTITION  part2 VALUES (' Shanghai ', ' Nanjing ')  tablespace  part2_tb) ;)

3. 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 1:

CREATE TABLE hash_table (  col Number (8),  INF VARCHAR2 ()) 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 (+),    sal number   ) PARTITION by  HASH (empno) Partitions 8STORE 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.

4. 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 (Ten), STATUS VARCHAR2 ()) 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)          )

5. 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) NOT NULL, item_description varchar2 (+), t Ransaction_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

1) Adding partitions

The following code adds a P3 partition to the sales table

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 ');

2) Delete 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.

3) Truncate 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;

4) Merging 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;

5) Split partition

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.

6) Mating Zone (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;

7) Renaming table partitions

The following code changes P21 to P2

ALTER TABLE SALES RENAME PARTITION P21 to P2;

8) Related inquiries

Cross-partition queries

How many partitions are on the query table

Querying index information

--Displays information about all partitioned tables in the database:

--Displays all partition table information that the current user can access:

--Displays information about all the partition tables for the current user:

--Display table partition information displays detailed partition information for all partitioned tables in the database:

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

--Displays detailed partitioning information for all partition tables for the current user:

--Display sub-partition information displays sub-partition information for all the combined partition tables of the database:

--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:

--Displays the partition column information for all partition tables for the current user:

--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:

--Displays sub-partition column information for all partitioned tables of the current user:

--How to query out all the partitioned tables in the Oracle database

--deleting data from a table is

--Delete partition table data for a partition is

Oracle Table Partitioning