This article from the following aspects to collate the concept and operation of the partition table:
1. Table space and the concept of partitioned tables
2. The specific role of table partitioning
3. Advantages and disadvantages of table partitioning
4. Table partitioning of several types and operating methods
5. Maintenance operations on the table partition.
(1) Table space and the concept of partitioned table
Tablespace: is a collection of one or more data files, all of which are stored in a specified table space, but are primarily stored as tables, so they are called table spaces.
Partition table:
When the amount of data in a table increases, the query data slows down, and the application's performance drops, 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 when querying the data, it does not scan the entire table every time.
(2). The specific role of table partitioning
Oracle's table partitioning capabilities provide great benefits for 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 a gigabit data system or a hyper-high-availability system.
Partitioning enables you to further subdivide a table, index, or index organization table into segments, which are sections of the database objects called partitions. Each partition has its own name, and you can choose your own storage attributes. From a database administrator's point of view, an object with a partition has multiple segments, which can be managed collectively or separately, giving the database administrator considerable flexibility in managing the objects after the partition. However, from an application perspective, the partitioned table is exactly the same as a partitioned table, and the SQL DML command is used to access the partitioned table without any modification.
When to use partitioned tables:
1, the size of the table more than 2GB.
2, the table contains historical data, new data is added to the new partition.
(3). Advantages and disadvantages of table partitioning
Table partitioning has the following advantages:
1, improve query performance: The query on the partition object can only search their own care, improve the speed of retrieval.
2. Enhance usability: If a partition of a table fails, the data in other partitions is still available;
3, Maintenance Convenience: If the table of a section of the fault, need to repair the data, only repair the partition can;
4, balanced I/O: You can map different partitions to disk to balance I/O, improve the overall system performance.
Disadvantages:
Partition Table correlation: Existing tables do not have methods that can be directly converted into partitioned tables. However, Oracle provides the ability to redefine tables online.
(4). Several types and operation methods of table partitioning
A. Range Zoning:
A range partition maps data to each partition based on scope, which is determined by the partitioning key that you specify when you create the partition. This partitioning method is most commonly used, and the partitioning key often takes a date. For example, you might be able to 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 bound value that is not included in the partition. Any record of a partition key that is equal to or greater than this upper bound value is added to the next higher partition.
2. All partitions, except the first one, will have an implicit lower bound value, which is the upper bound value 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 any partition key in other partitions, and can be understood to be higher than the value less then specified in any partition, including null values.
Example one:
Suppose there is a customer table with 200000 rows of data, we partition the 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 tables and partitions, 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
)
Case 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 (1000) tablespace part1_tb,
PARTITION part2 VALUES less THEN (MAXVALUE) tablespace PART2_TB
);
Two. List partition:
The feature of the partition is that there are only a few values in a column, and we can use a list partition based on this feature.
Example One
CREATE TABLE Problem_tickets
(
PROBLEM_ID Number (7) is 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
Case II
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 partition uses a hashing algorithm on the column value to determine which partition to put the row into. A hash partition is recommended when the value of a 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 these partitions are identical in size by hashing partitions 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);
The main mechanism of the hash partition is based on the hash algorithm to calculate a specific record should be inserted into which partition, the hash algorithm is the most important hash function, Oracle if you want to use the hash partition, you can only specify the number of partitions. It is recommended that the number of partitions should be 2 n-th, so that the data distribution among the partitions is more uniform.
Four. Combined range hash Partition
This partition is based on a range partition and a list partition, where the table is first scoped by a column, and then the 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 a range partition and a hash partition, the table is first scoped by a column, and then a column for the hash partition.
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 on table partitioning:
One, add partitions
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 partition boundaries added above should be higher than the last partition boundary.
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 deletes the P3 table partition:
ALTER TABLE SALES DROP PARTITION P3;
The P4SUB1 sub partition was deleted in the following code:
ALTER TABLE SALES DROP subpartition p4sub1;
Note: If the deleted partition is the only partition in the table, then the partition will not be deleted and the table must be deleted to remove the partition.
Iii. Truncation of partitions
Truncating a partition means deleting the data from a partition and does not delete the partition, nor does it delete the 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 child partition with the following code:
ALTER TABLE SALES TRUNCATE subpartition p2sub2;
Iv. Merging of partitions
Merge partitions combine adjacent partitions into one partition, resulting partitions with higher partition boundaries, and it is noteworthy 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. Split Division
A split partition splits a partition into two new partitions, and the original partition does not exist until it is split. 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);
Vi. junction Zoning (Coalesca)
Combined partitioning is the integration of data from the hash partition into other partitions, and when the data in the hash partition is larger, the hash partition can be added and then jointed, and it is noteworthy that the junction partition can only be used in the hash partition. Splice partitions through the following code:
ALTER TABLE SALES Coalesca PARTITION;
Vii. Renaming table Partitions
The following code changes P21 to P2
ALTER TABLE SALES RENAME PARTITION P21 to P2;
Viii. 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 for all partitioned tables in the database:
SELECT * FROM Dba_part_tables
--Displays all partition table information accessible to the current user:
SELECT * FROM All_part_tables
--Displays information about all partitioned 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 zoning information for all partitioned tables accessible to the current user:
SELECT * FROM All_tab_partitions
--Displays detailed partition information for all partitioned tables for the current user:
SELECT * FROM User_tab_partitions
--Displays the child partition information displays the child partition information of all the combined partition tables in the database:
SELECT * FROM Dba_tab_subpartitions
--Displays the child partition information for all combined partitioned tables accessible to the current user:
SELECT * FROM All_tab_subpartitions
--Displays the child partition information for all grouped partitioned tables for the current user:
SELECT * FROM User_tab_subpartitions
--Display the partition column to display the partition column information for all the partitioned tables in the database:
SELECT * FROM Dba_part_key_columns
--Displays the partition column information for all partitioned tables accessible to the current user:
SELECT * FROM All_part_key_columns
--Displays the partition column information for all the current user's partitioned tables:
SELECT * FROM User_part_key_columns
--Displays the child partition column to display the child partition column information of all partitioned tables in the database:
SELECT * FROM Dba_subpart_key_columns
--Displays the child partition column information for all partitioned tables accessible to the current user:
SELECT * FROM All_subpart_key_columns
--Displays the child partition column information for all partitioned tables for the current user:
SELECT * FROM User_subpart_key_columns
--How to query 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;
--The data that deletes a partition of a partitioned table is
ALTER TABLE TABLE_NAME TRUNCATE PARTITION P5;
PS: The table row movement permission must be assigned when update changes the partition to which the data belongs.
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 insert new partition, new data update, the source old data deletion steps, so rowid will change; Data indexes will also be redirected.
Turn from: Author: Run Ming http://blog.csdn.net/runming918
